Support #[frb(generate_impl_enum)] ; Fix overriding attributes in third party crates for traits

[fzyzcjy]

Changes

Please list issues fixed by this PR here, using format "Fixes #the-issue-number".

Checklist

• An issue to be fixed by this PR is listed above.
• New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
• ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
• If this PR adds/changes features, documentations (in the ./website folder) are updated.
• CI is passing. Please refer to this page to see how to solve a failed CI.

Remark for PR creator

• ./frb_internal --help shows utilities for development.
• If fzyzcjy does not reply for a few days, maybe he just did not see it, so please ping him.

[codecov]

Codecov Report

Attention: Patch coverage is 96.50735% with 19 lines in your changes missing coverage. Please review.

Project coverage is 96.95%. Comparing base (76cdb39) to head (e6b38f3).

Files	Patch %	Lines
...degen/src/library/utils/basic_code/general_code.rs	71.15%	15 Missing ⚠️
.../src/library/utils/basic_code/simple_code_trait.rs	90.47%	2 Missing ⚠️
...egen/src/library/codegen/generator/api_dart/mod.rs	91.66%	1 Missing ⚠️
...n/src/library/codegen/generator/misc/path_texts.rs	98.14%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2046      +/-   ##
==========================================
- Coverage   98.25%   96.95%   -1.31%     
==========================================
  Files         453      459       +6     
  Lines       17807    18095     +288     
==========================================
+ Hits        17497    17544      +47     
- Misses        310      551     +241     

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