refactor: Fix linting, testing, CI, remove old backends and logs

[bmtcril]

Long overdue cleanup and basic testing so we can be more confident about requirements updates. Manually tested against all 3 remaining backends successfully.

[pomegranited]

👍 couple of minor nits, but this this is good to merge once they're addressed or dismissed.

Thank you for culling out the unneeded mongo and citus backends, as well as all of those log files! Leaner and meaner tool now..

• I tested this by running this branch in my Aspects shell, on both the ralph and clickhouse backends.
• I read through the code
• I checked for accessibility issues N/A
• Includes documentation
• Commit structure follows OEP-0051

[pomegranited]

Can we remove the install_requires for pymongo[srv] and psycopg2-binary too?

Alternatively, borrow this: https://github.com/overhangio/tutor/blob/master/setup.py#L60

[bmtcril]

The way Tutor does it has some issues with the OeX constraints and version pinning, but I removed those and matched the pinned versions in base.in. I also removed the numpy requirement since it seems like clickhouse-connect no longer throws an error when it's missing, and widened the constraint to <0.7 since it's been running 0.6.4 fine based off of the previous non-pinned versioning in setup.py. I'm not 100% sure this won't break things, but I also version bumped so we can test in the Aspects plugin and roll back if necessary.

[Ian2012]

LGTM, tested with a fresh environment