Implement Upsert methods for weakMap: getOrInsert and getOrInsertComputed

[rrogerc]

This Pull Request closes #4435, implementing the Upsert proposal for weak map

It changes the following:

• Adds WeakMap.prototype.getOrInsert method.
• Adds WeakMap.prototype.getOrInsertComputed method.
• Enforces object-only keys and callable callbacks.
• Includes new tests for both methods to ensure correct behavior and reentrancy.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.55%. Comparing base (6ddc2b4) to head (9358a81).
⚠️ Report is 556 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4459      +/-   ##
==========================================
+ Coverage   47.24%   51.55%   +4.30%     
==========================================
  Files         476      504      +28     
  Lines       46892    51454    +4562     
==========================================
+ Hits        22154    26525    +4371     
- Misses      24738    24929     +191     

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[jedel1043]

Everything looks nice! I just have a couple of suggestions to improve the code.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	50,595	50,595	0
Passed	47,620	47,635	+15
Ignored	2,056	2,056	0
Failed	919	904	-15
Panics	0	0	0
Conformance	94.12%	94.15%	+0.03%

Fixed tests (15):

test/staging/upsert/WeakMap/getOrInsertComputed/returns-value-if-key-is-present-object-key.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/length.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/adds-object-element.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/adds-value-different-callbackfn.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/callbackfn-throws.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/not-a-constructor.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/getOrInsertComputed.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/overwrites-mutation-from-callbackfn.js (previously Failed)
test/staging/upsert/WeakMap/getOrInsertComputed/returns-value-if-key-is-not-present-object-key.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/getOrInsert.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/returns-value-if-key-is-present-object-key.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/length.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/adds-object-element.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/not-a-constructor.js (previously Failed)
test/built-ins/WeakMap/prototype/getOrInsert/returns-value-if-key-is-not-present-object-key.js (previously Failed)

[jedel1043]

Very nice, it looks great!

You may need to rebase the PR though, but we can merge after that.