Clickhouse-connect

instead of being passed as ClickHouse server settings. This is in conjunction with some refactoring in Client construction.
The supported method of passing ClickHouse server settings is to prefix such arguments/query parameters with`ch_`.

Bug Fixes
- Don't send a setting value if the setting is already correct according to the `system.settings` table.
Closes https://github.com/ClickHouse/clickhouse-connect/issues/469
- Ensure that the http `user_agent` header is in ascii. Note this could lead to an incorrectly encoded `os_user` if the
os_user is not an Ascii string. Closes https://github.com/ClickHouse/clickhouse-connect/issues/484
- Fix "cannot access local variable" exception where the http client encounters an unexpected streaming error. Also
log that unexpected streaming error to assist debugging. Closes https://github.com/ClickHouse/clickhouse-connect/issues/483
- Check that arrow/pandas is installed when calling `query_df` and `query_arrow` and raise a more meaningful exception
if the required library is absent. Closes https://github.com/ClickHouse/clickhouse-connect/issues/477

Improvements
- Some typing hints have been corrected. Thanks to [Avery Fischer](https://github.com/biggerfisch) for the PR!
- The docker based tests have been fixed to work with security improvements in recent ClickHouse releases
- Query string cleanup is now (in theory) microseconds faster. Thanks to [Sviatoslav Bobryshev](https://github.com/sbobryshev)
for the optimization

Bug Fix
- The async client was not shutting down its associated executor thread pool, result in a memory leak if multiple
async clients were created. Closes https://github.com/ClickHouse/clickhouse-connect/issues/424. Note that the `close`
function for the async client is now async to cleanly close down the pool. The recommended way to use an async client
is now within an AsyncContext. See the associated [PR](https://github.com/ClickHouse/clickhouse-connect/pull/457) for details.
Thanks to ClickHouse core developer pufit for the fix!

Bug Fix
- Fix an edge case where a Pandas dataframe that contains _only_ Int64 (or smaller) values would cause an exception when
inserting into a ClickHouse "big int" table of U/Int128/256. Closes https://github.com/ClickHouse/clickhouse-connect/issues/452

Bug Fix
- Fix missing default for new access_token parameter. Thanks to [Lukas Thaler](https://github.com/lukasthalerINNIO) for the PR.

Improvement
- Added support for JWT authentication (ClickHouse Cloud feature).
It can be set via the `access_token` client configuration option for both sync and async clients.
The token can also be updated via the `set_access_token` method in the existing client instance.
NB: do not mix access token and username/password credentials in the configuration;
the client will throw an error if both are set.