Automatically mark methods of non-pub structs as ignored

[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 94.80519% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 98.38%. Comparing base (9cc246c) to head (977a7e1).
Report is 1 commits behind head on master.

❗ Current head 977a7e1 differs from pull request most recent head f2c24bd

Please upload reports for the commit f2c24bd to get more accurate results.

Files	Patch %	Lines
...ary/codegen/parser/mir/function_parser/argument.rs	20.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2012      +/-   ##
==========================================
- Coverage   98.38%   98.38%   -0.01%     
==========================================
  Files         410      410              
  Lines       16728    16792      +64     
==========================================
+ Hits        16458    16520      +62     
- Misses        270      272       +2     

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