Implement [[HostDefined]] field on Realms

[HalidOdat]

It changes the following:

• Add [[HostDefined]] field to Realms
• Add example.
• Make FunctionObjectBuilder take a Realm instead of Context

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	95,574	95,574	0
Passed	75,084	75,084	0
Ignored	19,494	19,494	0
Failed	996	996	0
Panics	0	0	0
Conformance	78.56%	78.56%	0.00%

[codecov]

Codecov Report

Patch coverage: 5.44% and project coverage change: -0.15% ⚠️

Comparison is base (8a78061) 50.31% compared to head (8595932) 50.17%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2952      +/-   ##
==========================================
- Coverage   50.31%   50.17%   -0.15%     
==========================================
  Files         436      438       +2     
  Lines       42604    42730     +126     
==========================================
  Hits        21438    21438              
- Misses      21166    21292     +126     

Files Changed	Coverage Δ
boa_cli/src/debug/limits.rs	0.00% <0.00%> (ø)
boa_cli/src/debug/optimizer.rs	0.00% <0.00%> (ø)
boa_engine/src/builtins/async_generator/mod.rs	30.57% <0.00%> (ø)
boa_engine/src/builtins/intl/collator/mod.rs	5.55% <0.00%> (ø)
.../src/builtins/iterable/async_from_sync_iterator.rs	11.30% <0.00%> (ø)
boa_engine/src/builtins/proxy/mod.rs	11.76% <0.00%> (ø)
boa_engine/src/context/mod.rs	55.55% <0.00%> (ø)
boa_engine/src/host_defined.rs	0.00% <0.00%> (ø)
boa_engine/src/lib.rs	73.33% <ø> (ø)
boa_engine/src/module/mod.rs	3.20% <0.00%> (ø)
... and 18 more

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[nekevss]

I still need to look at this a little deeper, but overall this looks pretty good. Just a couple questions/comments.

[raskad]

Looks good

[HalidOdat]

I redesigned the [[HostDefined]] API, the reason being that, when I was looking through the fetch WebAPI spec and realized that they utilize storing custom state. This wouldn't be a problem if it was implemented in boa_engine (since we could add it to realm if we wanted), but since we have an external crate for some WebAPI stuff (boa_runtime). It would occupy the host defined field and the user would not be able to create their own state.

That's why It's been extended to work with as many type Ts that implement NativeObject in a registry, with the key being the TypeId

[jedel1043]

Really liking the new API! And it's also pretty similar to the upcoming Provider API (rust-lang/rust#96024), so we could migrate to that in the future without changing the API

[raskad]

I also like the API. Just found a few typos in the example, otherwise I'm for merging this.

[jedel1043]

Looks good!