feat: Add code for computing service coverage windows and trip counts

[bdferris-v2]

Adds TripCalendarUtil, which provides methods for computing service coverage windows based on daily trip counts.
Will hopefully be useful for #886 and PR #1289.

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[briandonahue]

LGTM! @bdferris-v2 Thank you for this - I will incorporate this into my PR. @isabelle-dr What is the appropriate way of merging - merge into master and then merge master into PR #1289, or merge this into #1289 and close this one?

[github-actions]

✅ Rule acceptance tests passed.
New Errors: 0 out of 1419 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
Dropped Errors: 0 out of 1419 datasets (~0%) are invalid due to code change, which is less than the provided threshold of 1%.
0 out of 1419 sources (~0 %) are corrupted.
Commit: c1ead9a
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.

[briandonahue]

@davidgamez @isabelle-dr Could someone take a look and merge this so that I can use it in #1289?

[davidgamez]

LGTM!

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[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%.
0 out of 1420 sources (~0 %) are corrupted.
Commit: 47ea948
Download the full acceptance test report here (report will disappear after 90 days).
✅ Rule acceptance tests passed.