Updates to new pytest framework

[dbeatty10]

related to #105 and #109

Description

Consolidated test files across adapters.

Trade-offs

The main difference in implementation here is separate pytest folders for each adapter or a single pytest folder for all adapters.

Single folder pros

• tests only need to be defined once and then used across all three adapters

Single folder cons

• more time-consuming later to split apart the adapters into separate code bases

Separate folders pros

• makes it a lot easier to customize tests per adapter
• allows nice syntax when skipping a particular test:
  • e.g., @pytest.mark.skip(reason="Ephemeral materializations not supported for MySQL 5.7")

Separate folders cons

• tests need to be redefined for each of the three adapters

Neither here nor there

Both single folder and separate folders can accommodate the following:

• allowing the profiles to be defined once in tests/conftest.py and then re-used in each test_*.py module

Decision

This decision could easily go either way.

Ultimately deciding to use a single folder with shared tests across all three adapters because:

• the MySQL 5.7 is end-of-life (EOL) in October, 2023 which will bring the number of adapters down to two anyways
• we will still retain the ability to split things up whenever we want to

Checklist

• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] I have updated the CHANGELOG.md with information about my change