lib: add Iterator global to primordials, improve iteration object coverage in frozen intrinsics

[Renegade334]

lib: add Iterator global to primordials

iterator_helpers is unflagged in V8 from v24.x.

lib: improve control abstraction coverage in frozen intrinsics

Adds the new internal iteration prototypes (%IteratorHelperPrototype%, %WrapForValidIteratorPrototype%) to frozen intrinsics, and improves/deduplicates coverage of iterator/generator objects.

Note that %AsyncFromSyncIteratorPrototype% is missing from the iterator spec – this is unresolvable AFAICT.

[bakkot]

Note that %AsyncFromSyncIteratorPrototype% is missing from the iterator spec – this is unresolvable AFAICT.

Indeed:

Async-from-Sync Iterator objects are never directly accessible to ECMAScript code.

It's a spec fiction used for defining behavior of other algorithms (for-await over a sync iterator, specifically), not a real thing (although engines might choose to have an internal representation of it for ease of implementation).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.35%. Comparing base (39b481b) to head (00e4207).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63698      +/-   ##
==========================================
- Coverage   91.96%   90.35%   -1.61%     
==========================================
  Files         379      732     +353     
  Lines      166638   236691   +70053     
  Branches    25497    44583   +19086     
==========================================
+ Hits       153242   213867   +60625     
- Misses      13099    14563    +1464     
- Partials      297     8261    +7964     

Files with missing lines	Coverage Δ
lib/internal/freeze_intrinsics.js	97.05% <100.00%> (+0.08%)	⬆️
lib/internal/per_context/primordials.js	99.20% <100.00%> (+17.14%)	⬆️

... and 476 files with indirect coverage changes

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