remove comment argument from Backend.log_migration

This argument is unused, and removing it from the insert query parameters fixes
the follow-up issue noted on #102
tests: ensure backends are always accessed as a contextmanager

This ensures that backends are cleaned up and the connection closed at the end
of tests, helping improve isolation between tests
fix sqlite3 deprecation warnings under python 3.12
oracle: add workaround for presence of database param in list_tables query

Fixes #101
quote all identifiers used in internal sql queries

This should fix #102 as well as future-proof against similar issues arising for
other backends
fix return value of change_param_style when bind_parameters is None

Fixes #100
doc: fix path to sphinx
fix broken doc build
docs: fix repo URL

fixes #99
fix deprecation warnings associated with usage of datetime.utcnow

fixes #96
bump major version number

Because this version breaks backwards compatibility for Python 3.8 users
tests: add python 3.12 and drop 3.7, 3.8

Python 3.7 is now EOL.

Python 3.8 support breaks with the recent switch to use importlib for migration
discovery. Given that Python 3.8 will be EOL in a few months too I'm not
inclined to put in the effort to make the new code compatible – users can
continue to use an old release if py38 support is required.
ensure files accessed through importlib.resources are cleaned up at exit
code formatting
Fixes Issues #94 #96

pkg_resources is deprecated see:
This throws a warning on every currently supported python version.
Additionally this breaks yoyo migrate if not manually installed setuptools, which currently isn't a dependcy.

This PR remove the dependency to pkg_resources resolving this issue.
docs: fix path to sphinx
Bump version number for dev
Added tag v8.2.0-release for changeset 6addbc6e66c9
Bump version number for release v8.2.0
Mark changelog with release date for v8.2.0