Scrapli-netconf

- Convert netconf 1.1 chunk handling over to the scrapligo style/way -- fixes 131 with thanks to
[Matt Takacs](https://github.com/matthewtakacs) for the help!

- Handle parsing out control characters that seem to pop up on some JunOS boxes with at least ssh2 transport, see 127.
- Hopefully improved some handling with possible "over reading" during initial session establishment. See 122 for a
lot of history on this one, and 126 for at least a partial fix (if not full fix?!)
- Thanks to [sanjmonkey](https://github.com/sanjmonkey) for expanding support for "with-defaults" parsing from
capabilities in 129

- Thank you to the very awesome [dmulyalin](https://github.com/dmulyalin) for adding support for commit-confirmed
in 97!
- Some other things, I'm sure of it... if nothing else just housekeeping things... if we've missed something you
added in here, let us know and it will get added!

- Removed deprecated `filters` argument
- Removed deprecated `NetconfScrape` and `AsyncNetconfScrape`
- Improved `raise_for_status` exception messages, see 92 and 90
- Dropped Python3.6 support as it is now EOL! Of course, scrapli probably still works just fine with 3.6 (if you
install the old 3.6 requirements), but we won't test/support it anymore.

- Force system transport ssh connections to allocate a tty (-tt); fixes issue that would prevent system transport
from sending any command > 1024 chars.
- Added `use_compressed_parser` argument to the driver constructor -- defaults to `True` which means we "squish" all
the whitespace out of any input we get from the user before sending it to the netconf server, generally this is no
problem, but some devices (looking at you NX-OS!) lock up and stop reading at some character counts (4096 in NX-OS
it seems) causing the connection to timeout and die. By *not* "squishing" whitespace out this does not happen.
- Fixed some typing issues and pinned to scrapli pre-release to take advantage of updated typing/packaging setup
- Deprecate `filters` argument on `get_config` -- will be supported (by decorator) until 2022.01.30 (and
pre-releases). This was done to make the arguments consistent for `get`, `get_config`, and `rpc`.
- Better handling of multiple filter elements in a filter string
- Smarter message building -- previously most of the final bytes payload that we send to the servers got built in
the base driver class, and then some more (1.1 encoding) got added in the channel base class -- silly! Fixed this,
so it is all done in the driver which eliminated a bunch of duplication (yay!).
- Deprecating `comms_ansi` -- see also scrapli changelog for this release (2021.07.30) for more details. This was
never used here in scrapli_netconf so should be a non issue, but will not be fully deprecated until 2022.01.30.
- Re-fix 10... see 68 -- now there is a test with a comment so I don't break this again :)
- Added `copy_config` method, thanks to Roman Dodin for adding this in scrapligo first!
- Added handling/warning about `use_compressed_parser` if we catch a timeout exception when looking for prompt after
writing inputs -- since I don't know (can't know?) which platforms may require this flag set to False this seems
like a reasonable way to let users know and point them in the right direction to get things working!
- Reswizzled the echo check to be like the scrapligo version -- much simpler/less moving parts, so should be good!

- Big overhaul in line with the scrapli core overhaul... mostly this was about reconciliation of the channel and
transport things and putting stuff where it should have been in the first place... see the changelog at scrapli
core for much more details
- *FUTURE BREAKING CHANGE* -- `NetconfScrape` and `AsyncNetconfScrape` have been renamed to `NetconfDriver` and
`AsyncNetconfDriver` -- there are alias classes so you can continue to use `NetconfScrape` and
`AsyncNetconfScrape` but there is a warning, and these will be removed at some point in the future!