Introduce a Class map

[jedel1043]

Related to #3314.

This change improves the ergonomics of the Class API by adding a class map that can be used to fetch the constructor and prototype of a registered class. This also slightly improves its API by implementing some missing features like using symbols as method names.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,574	95,574	0
Passed	75,193	75,193	0
Ignored	19,482	19,482	0
Failed	899	899	0
Panics	0	0	0
Conformance	78.68%	78.68%	0.00%

[codecov]

Codecov Report

Attention: 86 lines in your changes are missing coverage. Please review.

Comparison is base (70ee050) 49.72% compared to head (ddd6bad) 49.68%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3315      +/-   ##
==========================================
- Coverage   49.72%   49.68%   -0.04%     
==========================================
  Files         443      443              
  Lines       43378    43410      +32     
==========================================
  Hits        21570    21570              
- Misses      21808    21840      +32     

Files	Coverage Δ
boa_engine/src/builtins/intl/segmenter/segments.rs	16.27% <100.00%> (-1.91%)	⬇️
boa_engine/src/builtins/iterable/mod.rs	70.76% <100.00%> (-0.66%)	⬇️
boa_engine/src/builtins/regexp/mod.rs	63.28% <100.00%> (-0.30%)	⬇️
boa_engine/src/builtins/string/mod.rs	57.49% <100.00%> (-0.11%)	⬇️
boa_engine/src/string/common.rs	48.48% <ø> (ø)
boa_engine/src/context/intrinsics.rs	97.28% <0.00%> (-0.30%)	⬇️
boa_engine/src/host_defined.rs	0.00% <0.00%> (ø)
boa_engine/src/object/mod.rs	30.29% <60.00%> (-0.12%)	⬇️
boa_examples/src/bin/classes.rs	0.00% <0.00%> (ø)
boa_engine/src/symbol.rs	67.36% <57.14%> (-2.91%)	⬇️
... and 4 more

... and 1 file with indirect coverage changes

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[HalidOdat]

Looks great! Just some comments, they don't block merging though :)

[HalidOdat]

Looks perfect to me! :)