Implement synthetic modules

[jedel1043]

Depends on #3292.

This Pull Request closes #3224.

It changes the following:

• Implements Synthetic Modules per the JSON modules proposal.
• Improves some patterns by using Gc::new_cyclic.

@HalidOdat I had to do a weird hack to be able to push the ActiveRunnable without a CodeBlock available to create a CallFrame. Since you're currently refactoring the VM, I didn't want to modify the definition of CallFrame to accommodate this special case. I could leave it as it is, of course, but would there be another way to store the ActiveRunnable inside the callstack without having to create a dummy CodeBlock in the process?

[HalidOdat]

We could wrap CodeBlock in an optional, but we will have to .expect on every access to contents for ordinary functions.

We could take the v8 approach, and merge value stack with frame stack, have different types of call frames (though this may need some unsafe)

For now we can leave a TODO and resolve it once call refactor (#3295) is complete.

[jedel1043]

For now we can leave a TODO and resolve it once call refactor (#3295) is complete.

Sounds good! I already left a TODO on it.

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,574	95,574	0
Passed	75,342	75,342	0
Ignored	19,482	19,482	0
Failed	750	750	0
Panics	0	0	0
Conformance	78.83%	78.83%	0.00%

[codecov]

Codecov Report

Attention: 252 lines in your changes are missing coverage. Please review.

Comparison is base (afb9283) 46.05% compared to head (88874ae) 45.86%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3294      +/-   ##
==========================================
- Coverage   46.05%   45.86%   -0.20%     
==========================================
  Files         474      477       +3     
  Lines       48742    48944     +202     
==========================================
  Hits        22450    22450              
- Misses      26292    26494     +202     

Files	Coverage Δ
boa_engine/src/lib.rs	73.33% <ø> (ø)
boa_examples/src/bin/modules.rs	0.00% <ø> (ø)
boa_engine/src/module/source.rs	0.00% <0.00%> (ø)
boa_engine/src/module/mod.rs	0.00% <0.00%> (-3.20%)	⬇️
boa_engine/src/module/loader.rs	10.90% <10.90%> (ø)
boa_examples/src/bin/synthetic.rs	0.00% <0.00%> (ø)
boa_engine/src/module/synthetic.rs	0.00% <0.00%> (ø)

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[HalidOdat]

Nice work! Looks good to me! :)

[raskad]

Nice work and great example :)