Fix test cases related to logging

[arnaudsjs]

Description

Same PR as https://github.com/inmanta/inmanta-core/pull/8153 but applied on the iso7 branch due to a merge conflict.

This PR fixes the logging-related test cases that broke due to https://github.com/inmanta/inmanta-core/commit/fc81b36711235eb10bf9aa0a4764b8422d42d34a.

Root cause of failures:

The above-mentioned commit made sure that the root log level is not changed by the apply_config() method. This broke the logging-related test cases because they assume that they can change the root log level.

Changes made by this PR:

• Add allow_overriding_root_log_level fixture that makes sure that the apply_config can change the root log level.
• Simplify the InmantaLoggerConfig.clean_instance() method. In the previous implementation it made a call to logging.shutdown(), which closes all the handlers. This PR re-adds that method invocation to simplify the method. This is not an issue for pytest, because pytest re-adds their handlers after each test case.

Self Check:

• [ ] Attached issue to pull request
• [ ] Changelog entry
• [x] Type annotations are present
• [x] Code is clear and sufficiently documented
• [x] No (preventable) type errors (check using make mypy or make mypy-diff)
• [x] Sufficient test cases (reproduces the bug/tests the requested feature)
• [x] Correct, in line with design
• [ ] End user documentation is included or an issue is created for end-user documentation
• [ ] If this PR fixes a race condition in the test suite, also push the fix to the relevant stable branche(s) (see test-fixes for more info)

[inmantaci]

Processing this pull request

[inmantaci]

Merged into branches iso7 in d4b3f218d8fbf95f0e25d04435488bb64f1c4400