fix: allow deriving both TryFromJs and TryIntoJs with custom converters

[mansiverma897993]

Closes #5361

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	53,125	53,125	0
Passed	51,072	51,072	0
Ignored	1,482	1,482	0
Failed	571	571	0
Panics	0	0	0
Conformance	96.14%	96.14%	0.00%

Tested main commit: 7ce9cae84ac9bf54fe528bb05b997ac24af808a4
Tested PR commit: 6be840340d15d25f64cde808b7304d1e16034924
Compare commits: 7ce9cae...6be8403

[codecov]

Codecov Report

❌ Patch coverage is 0% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.23%. Comparing base (6ddc2b4) to head (6be8403).
⚠️ Report is 989 commits behind head on main.

Files with missing lines	Patch %	Lines
core/macros/src/lib.rs	0.00%	17 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5403       +/-   ##
===========================================
+ Coverage   47.24%   60.23%   +12.98%     
===========================================
  Files         476      567       +91     
  Lines       46892    63160    +16268     
===========================================
+ Hits        22154    38042    +15888     
- Misses      24738    25118      +380     

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[jedel1043]

Seems like the best thing we can do right now. We might want to change syntax a bit to be something like boa_try_from_js(with = "function") to avoid code duplication, but that's just a future enhancement IMO. Thanks!

[mansiverma897993]

@jedel1043
Thanks for the suggestion! I've updated the syntax to use #[boa_try_from_js(with = "...")] and #[boa_try_into_js(with = "...")] helper attributes respectively. This eliminates the need to parse and ignore each other's custom attributes, keeping the two macro derivations decoupled.