refactor(fixtures): Remove formats.py, embed properties as class vars

[marioevz]

🗒️ Description

Minor Major refactor to the ethereum_test_fixtures where each subclass of BaseFixture now contains all the properties of the format, and therefore ethereum_test_fixtures/formats.py is not longer necessary (nor is the Enum it defined).

FixtureFormats was widely used across many places in several libraries, hence the high number of files changed, but the changes are relatively minor.

🔗 Related Issues

None

✅ Checklist

• All: Set appropriate labels for the changes.
• All: Considered squashing commits to improve commit history.
• All: Added an entry to CHANGELOG.md. skipped
• All: Considered updating the online docs in the ./docs/ directory.
• Tests: All converted JSON/YML tests from ethereum/tests have been added to converted-ethereum-tests.txt.
• Tests: A PR with removal of converted JSON/YML tests from ethereum/tests have been opened.
• Tests: Included the type and version of evm t8n tool used to locally execute test cases: e.g., ref with commit hash or geth 1.13.1-stable-3f40e65.
• Tests: Ran mkdocs serve locally and verified the auto-generated docs for new tests in the Test Case Reference are correctly formatted.

[danceratopz]

Nice clean-up! In particular to fill's pytest_collection_modifyitems()! I'd just add a small comment to help the reader.

LGTM.