Remove unused class environments

[raskad]

Building on #3328 this removes a bunch of unneeded class environments that where more of a hack to get the class name binding in some places. This also enables removing the class_object from FunctionKind.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,574	95,574	0
Passed	75,273	75,273	0
Ignored	19,482	19,482	0
Failed	819	819	0
Panics	0	0	0
Conformance	78.76%	78.76%	0.00%

[raskad]

@HalidOdat let me know if you want to have #3322 merge before this, since the changes will cause some conflicts.

[codecov]

Codecov Report

Attention: 40 lines in your changes are missing coverage. Please review.

Comparison is base (55466b0) 49.43% compared to head (265a4c9) 49.51%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3332      +/-   ##
==========================================
+ Coverage   49.43%   49.51%   +0.08%     
==========================================
  Files         446      446              
  Lines       43873    43777      -96     
==========================================
- Hits        21688    21678      -10     
+ Misses      22185    22099      -86     

Files	Coverage Δ
boa_engine/src/builtins/function/mod.rs	39.81% <ø> (+0.24%)	⬆️
boa_engine/src/bytecompiler/function.rs	100.00% <ø> (+8.82%)	⬆️
boa_engine/src/vm/code_block.rs	50.29% <ø> (+0.68%)	⬆️
boa_engine/src/vm/flowgraph/mod.rs	0.00% <ø> (ø)
boa_engine/src/vm/opcode/define/class/getter.rs	0.00% <ø> (ø)
boa_engine/src/vm/opcode/define/class/method.rs	0.00% <ø> (ø)
boa_engine/src/vm/opcode/define/class/setter.rs	0.00% <ø> (ø)
boa_engine/src/vm/opcode/mod.rs	5.32% <ø> (ø)
boa_engine/src/vm/opcode/push/class/field.rs	0.00% <ø> (ø)
boa_engine/src/vm/opcode/push/class/private.rs	0.00% <ø> (ø)
... and 4 more

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[HalidOdat]

Nice refactor!

As for the merging, I think either way seems fine :)

[jedel1043]

Nice work! Opted for merging the other PR first because this seems like a simpler rebase.