Fix lexical environments in for loops

[raskad]

This Pull Request changes the following:

• Only push a new environment in for loops when the initializer is a LexicalDeclaration.
• Push a new environment for every iteration when let bindings are used in the initializer.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	94,657	94,657	0
Passed	73,889	73,901	+12
Ignored	17,505	17,505	0
Failed	3,263	3,251	-12
Panics	0	0	0
Conformance	78.06%	78.07%	+0.01%

Fixed tests (12):

test/language/statements/for/scope-body-lex-boundary.js [strict mode] (previously Failed)
test/language/statements/for/scope-body-lex-boundary.js (previously Failed)
test/language/statements/let/syntax/let-iteration-variable-is-freshly-allocated-for-each-iteration-single-let-binding.js [strict mode] (previously Failed)
test/language/statements/let/syntax/let-iteration-variable-is-freshly-allocated-for-each-iteration-single-let-binding.js (previously Failed)
test/language/statements/let/syntax/let-closure-inside-initialization.js [strict mode] (previously Failed)
test/language/statements/let/syntax/let-closure-inside-initialization.js (previously Failed)
test/language/statements/let/syntax/let-closure-inside-condition.js [strict mode] (previously Failed)
test/language/statements/let/syntax/let-closure-inside-condition.js (previously Failed)
test/language/statements/let/syntax/let-closure-inside-next-expression.js [strict mode] (previously Failed)
test/language/statements/let/syntax/let-closure-inside-next-expression.js (previously Failed)
test/language/statements/let/syntax/let-iteration-variable-is-freshly-allocated-for-each-iteration-multi-let-binding.js [strict mode] (previously Failed)
test/language/statements/let/syntax/let-iteration-variable-is-freshly-allocated-for-each-iteration-multi-let-binding.js (previously Failed)

[codecov]

Codecov Report

Merging #2917 (b6fe05c) into main (c827313) will increase coverage by 0.02%.
The diff coverage is 94.73%.

@@            Coverage Diff             @@
##             main    #2917      +/-   ##
==========================================
+ Coverage   51.98%   52.01%   +0.02%     
==========================================
  Files         431      431              
  Lines       43647    43669      +22     
==========================================
+ Hits        22690    22713      +23     
+ Misses      20957    20956       -1     

Impacted Files	Coverage Δ
boa_engine/src/bytecompiler/statement/loop.rs	84.08% <94.11%> (+1.55%)	⬆️
boa_ast/src/declaration/variable.rs	95.45% <100.00%> (+0.10%)	⬆️
boa_engine/src/vm/call_frame/env_stack.rs	96.82% <100.00%> (ø)

[nekevss]

Everything looks good to me, just a couple questions/thoughts

[HalidOdat]

Nice work!

[nekevss]

Nice work 😄