feat: Update acceptance test report to include changes in WARNINGS.

[bdferris-v2]

Refactor the acceptance test validation report comparison logic to consider changes to WARNING-level notices, not just ERRORs. We could more easily expand this to include INFO-level notices as well, if we so desire. Currently, this change does not cause automatic blocking of a change if the # of warnings changes significantly, but we could change that as well.

As part of this change, I refactored a bunch of logic out of ValidationReport and moved it into a new NoticeSet to be separate some concerns. I also refactored a bunch of references to "errors" to more generic "notices".

Closes #1349.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with gradle test to make sure you didn't break anything
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1420 sources (~0 %) are corrupted.
Commit: ad4009a
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[davidgamez]

LGTM!

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1420 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1420 sources (~0 %) are corrupted.
Commit: bd3a8b4
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[isabelle-dr]

Do we need to update https://github.com/MobilityData/gtfs-validator/blob/master/docs/ACCEPTANCE_TESTS.md as a result of this PR?