Make generated output sorted when using proxy_enum and trait_impl

[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

All modified and coverable lines are covered by tests ✅

Project coverage is 99.11%. Comparing base (e2a38d1) to head (e160864).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2115      +/-   ##
==========================================
+ Coverage   98.41%   99.11%   +0.70%     
==========================================
  Files         485      486       +1     
  Lines       19609    19656      +47     
==========================================
+ Hits        19298    19482     +184     
+ Misses        311      174     -137     

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