Tests for proposal-canonical-tz Stage 3 (will be merged into Temporal)

[justingrant]

This PR includes tests for the Time Zone Canonicalization proposal (proposal-canonical-tz) that reached Stage 3 at the July 2023 TC39 meeting.

At the same meeting, it was decided that this proposal should be merged into Temporal, so these tests are now part of tc39/proposal-temporal#2633.

Test roadmap

• DONE Add lightweight "Demitasse" tests in https://github.com/tc39/proposal-canonical-tz/blob/main/polyfill/test/canonicaltz.mjs that cover this proposal's full surface area.
• DONE Fix 15 existing Test262 tests that were broken by this proposal, because they assumed that time zone identifiers are always canonicalized.
• DONE: Migrate Temporal.TimeZone.p.equals (the only new API in this proposal) Demitasse tests to Test262.
• DONE: Migrate Temporal.TimeZone Demitasse tests to Test262.
• DONE: Migrate Temporal.ZonedDateTime Demitasse tests to Test262.
• DONE: Migrate Intl.DateTimeFormat Demitasse tests to Test262.

[ptomato]

Thanks! This matches my understanding of the proposal.

Looks like there's a merge conflict in features.txt, so it needs a rebase.

[justingrant]

Thanks for the review! I'll make the changes you recommend. Will try to get these changed before I present in 15 hours. :-)

[ptomato]

Thanks for the review! I'll make the changes you recommend. Will try to get these changed before I present in 15 hours. :-)

I don't think it's necessary to rush! Having test262 tests merged is a requirement for stage 4, but not 3. Anyway the comments are just minor 😄

[justingrant]

All review feedback is resolved in the latest fixup commits.

I'll autosquash them if this proposal achieves Stage 3 later tonight (my time), but figured that it'd be helpful to keep them separate for now so they're easier to review.

[justingrant]

@ptomato - let me know if you want to review the fixup commits that I made in response to your feedback. Otherwise I'll just rebase and autosquash them. Thanks!

[justingrant]

Marked as ready for review because this proposal reached Stage 3. Also made a few updates:

• Autosquashed older changes from reviews
• Reverted changes to features.txt because this proposal is being merged into Temporal
• Added cases to ensure handling of case-sensitive comparisons of custom time zone IDs
• Updated OP with link to Temporal PR (Normative: Merge proposal-canonical-tz Stage 3 into Temporal proposal-temporal#2633) that will include these tests.