Refactor Temporal Calendar API for AnyCalendar and fields

[nekevss]

This PR is related to the ongoing work for Temporal.

The largest change on this PR is primarily updating CalendarSlot.

// Old CalendarSlot
enum CalendarSlot {
    Identifier(String),
    Protocol(Box<dyn CalendarProtocol>),
}

// New CalendarSlot
enum CalendarSlot<C: CalendarProtocol> {
    Builtin(AnyCalendar),
    Protocol(C),
}

It changes the following:

• Switches CalendarSlot::Protocol(Box<dyn CalendarProtocol>) to CalendarSlot::Protocol(C).
• Switches CalendarSlot::Identifier(String) to CalendarSlot::Builtin(AnyCalendar)
• Updates CalendarProtocol to include fields and mergeFields.

I think there are still a couple things I want to double check/work through. But posting this as a draft in the meantime for any early feedback/thoughts.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,960	95,960	0
Passed	76,534	76,534	0
Ignored	18,477	18,477	0
Failed	949	949	0
Panics	0	0	0
Conformance	79.76%	79.76%	0.00%

[codecov]

Codecov Report

Attention: 471 lines in your changes are missing coverage. Please review.

Comparison is base (c2f145c) 48.97% compared to head (0ad2add) 48.83%.
Report is 10 commits behind head on main.

Files	Patch %	Lines
core/temporal/src/components/calendar.rs	9.75%	185 Missing ⚠️
core/temporal/src/fields.rs	0.00%	119 Missing ⚠️
core/engine/src/builtins/temporal/calendar/mod.rs	16.83%	84 Missing ⚠️
...re/engine/src/builtins/temporal/calendar/object.rs	0.00%	45 Missing ⚠️
core/engine/src/builtins/temporal/fields.rs	0.00%	21 Missing ⚠️
core/temporal/src/components/duration.rs	0.00%	3 Missing ⚠️
...ngine/src/builtins/temporal/plain_date_time/mod.rs	0.00%	2 Missing ⚠️
...ngine/src/builtins/temporal/plain_month_day/mod.rs	0.00%	2 Missing ⚠️
core/temporal/src/components/date.rs	50.00%	2 Missing ⚠️
core/temporal/src/components/zoneddatetime.rs	33.33%	2 Missing ⚠️
... and 5 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3522      +/-   ##
==========================================
- Coverage   48.97%   48.83%   -0.15%     
==========================================
  Files         471      470       -1     
  Lines       48498    48674     +176     
==========================================
+ Hits        23752    23769      +17     
- Misses      24746    24905     +159     

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[jedel1043]

Thanks to the new design, we can remove the unsafe_empty_trace and properly implement Trace for CalendarSlot<C: Trace>.

[nekevss]

Marking as ready for review as I believe the core changes for CalendarSlot<C> are complete. There are still a few things that could be improved on this branch, specifically around the functionality of new builtin calendars from AnyCalendar as well as CalendarDescriptorFields, CalendarFieldKeysToIgnore, and CalendarResolveField (I have a rough idea of what needs to be there, but just wanted to do some further research to confirm).

[HalidOdat]

Great work! :)

[raskad]

Looks good to me. I agree with @HalidOdat's comment but that should not block the merge :)