[Merged by Bors] - Implement var initializers in for-in loops

[jedel1043]

This Pull Request implements Initializers in ForIn Statement Heads from the Annex B. This also cleans up the "annex-b" feature to be able to disable it with --no-default-features, since I couldn't test the error messages when the feature is disabled.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	94,591	94,591	0
Passed	73,161	73,162	+1
Ignored	17,530	17,530	0
Failed	3,900	3,899	-1
Panics	0	0	0
Conformance	77.34%	77.35%	+0.00%

Fixed tests (1):

test/annexB/language/statements/for-in/nonstrict-initializer.js (previously Failed)

[codecov]

Codecov Report

Merging #2842 (0f9b268) into main (f97ad0d) will increase coverage by 0.00%.
The diff coverage is 47.94%.

@@           Coverage Diff           @@
##             main    #2842   +/-   ##
=======================================
  Coverage   50.92%   50.92%           
=======================================
  Files         419      419           
  Lines       41780    41805   +25     
=======================================
+ Hits        21278    21291   +13     
- Misses      20502    20514   +12     

Impacted Files	Coverage Δ
boa_parser/src/error.rs	59.09% <0.00%> (ø)
boa_parser/src/parser/statement/if_stm/mod.rs	51.61% <0.00%> (-0.85%)	⬇️
...oa_parser/src/parser/statement/labelled_stm/mod.rs	65.21% <25.00%> (-1.45%)	⬇️
...er/src/parser/statement/iteration/for_statement.rs	55.83% <43.47%> (-1.61%)	⬇️
boa_ast/src/statement/iteration/mod.rs	43.47% <50.00%> (+5.38%)	⬆️
boa_engine/src/bytecompiler/statement/loop.rs	81.32% <63.15%> (-0.68%)	⬇️
boa_parser/src/lexer/mod.rs	79.31% <100.00%> (ø)
boa_parser/src/parser/statement/variable/mod.rs	89.23% <100.00%> (+0.70%)	⬆️

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[HalidOdat]

Looks good to me! :)

[raskad]

bors r+

[bors]

Pull request successfully merged into main.

Build succeeded:

• Build and Test (macos-latest)
• Build and Test (windows-latest)
• Coverage
• Misc