Normative: Make CalendarDateWeekOfYear return undefined

[Aditi-1400]

Make CalendarDateWeekOfYear return undefined for all calendars without well-defined week calendar system

Fixes: #2744

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (737baf2) 96.56% compared to head (f5b3edb) 96.61%.

Files	Patch %	Lines
polyfill/lib/calendar.mjs	95.83%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2756      +/-   ##
==========================================
+ Coverage   96.56%   96.61%   +0.04%     
==========================================
  Files          23       23              
  Lines       12277    12309      +32     
  Branches     2271     2271              
==========================================
+ Hits        11855    11892      +37     
+ Misses        360      355       -5     
  Partials       62       62              

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[ptomato]

After initially reviewing this I thought of something else that needs to be done. We should change CalendarWeekOfYear and CalendarYearOfWeek so that a custom calendar's weekOfYear and yearOfWeek method can return undefined. (Similar to what we do in CalendarEra and CalendarEraYear.) This is also something we could write test262 tests for.

[ptomato]

👍 Thanks!

[ptomato]

This normative change reached consensus in the 2023-02 TC39 plenary meeting. I've updated this PR to include the test262 tests that I've just merged.