Scrapli

- Continued improvement around `SystemSSHTransport` connection/auth failure logging
- Fix for very intermittent issue where pty fd is not available for reading on SystemSSH/Telnet connections, now we loop over the select statement checking the fd instead of failing if it isn't immediately readable
- Implement atexit function if keepalives are enabled -- this originally just lived in the ssh2 transport, but needs to be here in the base `Transport` class as the issue affected all transport types
- Added `send_commands_from_file` method... does what it sounds like it does...
- Added `send_configs_from_file` method (`NetworkDriver` and sub-classes)... also does what it sounds like it does
- Simplified privilege levels and overhauled how auth escalation/deescalation works. Its still probably a bit more complex than it should be, but its a bit more efficient and at least a little simpler/more flexible.
- Removed `comms_prompt_pattern` from Network drivers and now build this as a big pattern matching all of the priv levels for that device type. This is used only for initial connection/finding prompt then scrapli still sets the explicit prompt for the particular privilege level.
- Implemented lru_cache on some places where we have repetitive tasks... probably unmeasurable difference, but in theory its a little faster now in some places
- Moved some Network driver things into the base `NetworkDriver` class to clean things up a bit.
- Added an `_abort_config` method to abort configurations for IOSXR/Juniper, this is ignored on the other core platforms
- *BREAKING CHANGE*: (minor) Removed now unneeded exception `CouldNotAcquirePrivLevel`
- Made the `get_prompt_pattern` helper a little worse... should revisit to improve/make its use more clear
- Fixed a screw up that had ridiculous transport timeouts -- at one point timeouts were in seconds, then milliseconds... went back to seconds, but left things setting millisecond values... fixed :D
- Added `transport_options` to base `Scrape` class -- this is a dict of arguments that can be passed down to your selected transport class... for now this is very limited and is just for passing additional "open_cmd" arguments to `SystemSSHTransport`. The current use case is adding args such as ciphers/kex to your ssh command so you don't need to rely on having this in an ssh config file.

- Increase character count for base prompt pattern for `Scrape`, `GenericDriver`, and core drivers. Example: `r"^[a-z0-9.\-()/:]{1,32}[>$]$"` for the base `IOSXEDriver` `comms_prompt_pattern` has been increased to: `r"^[a-z0-9.\-()/:]{1,48}[>$]$"`
- Improve the logging for `SystemSSHTransport` authentication
- Fixed an issue where `SystemSSHTransport` auth would fail due to a login banner having the word `password` in the banner/text
- Significantly increase the base `timeout_ops` value -- as this is not a timer that is going to cause things to block, it may as well be much higher for the default value to help prevent issues
- Fixed an issue w/ ssh config file not parsing the last host entry
- Added super basic tests for most of the examples -- just making sure they don't blow up... in general that should keep them in decent shape!
- Removed cssh2 and miko transports from scrapli core. These have been migrated to their own repositories. From a users perspective nothing really should change -- you can still `pip install scrapli[paramiko]` to install the paramiko transport and the requirements (paramiko), and the actual usage (setting `"transport" = "paramiko "`) remains the same! This is mostly about keeping the core of scrapli as simple as possible, and also will hopefully help to illustrate that `SystemSSH` is the development priority for scrapli.
- Convert many function calls to use keyword args for better readability throughout
- Add a `comms_auto_expand` argument to the `Channel`; for now this is mostly not used, but may be useful in the future. The purpose of this is to handle devices that auto expand input commands to their full canonical name.
- Hopefully(?) fixed a bit of an idiosyncrasy where the `timeout_transport` was being used to decorate read/write operations for telnet/system transports. This is no longer the case, the read/write methods are NOT decorated now , instead we rely on the `timeout_ops` to time these operations out OR the `timeout_transport` being set to the timeout value (telnet) or `ServerAliveInterval` value for system ssh.

- *BREAKING CHANGE*: modify `send_interact` to just make more sense in general... now it supports 1->N "events" to interact with -- see the "handling prompts" section of README for updated example
- Moved `record_response` of `Response` object to be a private method, shouldn't really be needed publicly
- Moved `authenticate` and `isauthenticated` methods of ssh2/paramiko transports to private methods
- Add `auth_bypass` option to ignore ssh auth for weird devices such as Cisco WLC -- currently only supported on system transport.
- Bump timeout_transport up to 10 seconds after finding some issues for some users.
- Add example for "non-standard" device type (Cisco WLC) demo-ing the auth_bypass, custom on_open method, custom comms_prompt_pattern and just general non-standard device stuff.
- Add option (and make it the default) to have textfsm data returned in list of dict form with the headers being the keys and of course the row values as the values, should be much nicer on the eyes this way!
- Added terminal width settings for the core drivers to set things as wide as possible so long commands don't have issues
- Teeny tiny improvements that may make things a tick faster in Channel by using str methods instead of re
- Create a draft of public api status doc -- this should be useful on a quick glance to see if/when any public methods change, obviously as development simmers down things should be stable but inevitably stuff *will* change, so the goal here is to just document when methods were introduced and the last time they were changed
- Move some imports around so that scrapli works on windows (with paramiko/ssh2 transports)

- Add support for `parse_genie` to Response object; obviously really only for Cisco devices at this point unless there are parsers floating around out there for other platforms I don't know about!
- Add an `atexit` function for the ssh2 transport which forcibly closes the connection. This fixes a bug where if a user did not manually close the connection (or use a context manager for the connection) the script would hang open until an interrupt.
- Added a `GenericDriver` for those with non-core platforms. The `GenericDriver` has a really broad prompt pattern match, doesn't know about privilege levels or any other device specific stuff, but does provide the `send_command `, `send_commands`, `send_interact`, and `get_prompt` methods just like the "core" drivers do. This should be a decent starting point for anyone working on non-core platforms!
- Minor unit test improvement to cover send_commands (plural) and to cover the new `GenericDriver`
- Improved auth failure handling for systemssh using pty auth (username/pass auth)
- Add "failed_when" strings to the core drivers; these are used in the response object to help indicate if the channel input failed or succeeded. For scrapli not super super helpful, but nornir_scrapli will benefit from this as well!
- Modify `NetworkDriver` to inherit from `GenericDriver` -- this allowed for some clean up of how/where `Response` objects get created/returned from. `Channel` now is much more de-coupled from whatever sits on top of it (this will be important for some netconf testing happening soon!).
- Minor test de-duplication around ssh config/known hosts file gathering.
- Added a few simple examples for structured data (textfsm/genie) and updated existing examples a bit.