Support #[frb(name)] on fields to rename them ; Automatically rename Dart field names if they conflict with Dart keywords

[fzyzcjy]

Changes

Close #2066

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 97.82609% with 1 line in your changes missing coverage. Please review.

Project coverage is 99.10%. Comparing base (c93793c) to head (71ebe0c).

Files	Patch %	Lines
frb_codegen/src/library/codegen/ir/mir/ident.rs	96.15%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2070   +/-   ##
=======================================
  Coverage   99.10%   99.10%           
=======================================
  Files         473      473           
  Lines       18919    18932   +13     
=======================================
+ Hits        18749    18762   +13     
  Misses        170      170           

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