feat: Validation for timeframes.txt

[bdferris-v2]

Per discussion in #1494, this PR adds support for validation of time-variable fares via timeframes.txt.

It specifically adds the following:

• Schema for timeframes.txt
• Validation of start_time and end_time: both must be present or not, neither greater than 24:00:00.
• Validation for timeframe overlap for timeframes in the same group and service id.
• Validation of the service_id reference.

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
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

[bdferris-v2]

@isabelle-dr wanted to call this PR out, in case you wanted to use it for timeframes.txt data validation or if you think I'm missing anything.

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1435 sources (~0 %) are corrupted.
Commit: a5f1fba
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
New Warnings: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Warnings: 0 out of 1435 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1435 sources (~0 %) are corrupted.
Commit: 3622011
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[davidgamez]

LGTM!