Automatically mirror for scanned third party types ; Skip generating auto accessors for borrowed fields

[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 60.48780% with 81 lines in your changes are missing coverage. Please review.

Project coverage is 97.85%. Comparing base (d67cada) to head (8f502b6).

Files	Patch %	Lines
frb_macros/src/components/attr_external.rs	0.00%	35 Missing ⚠️
frb_macros/src/components/converter.rs	0.00%	31 Missing ⚠️
.../library/codegen/parser/mir/function_parser/mod.rs	37.50%	5 Missing ⚠️
...brary/codegen/parser/mir/function_parser/output.rs	80.95%	4 Missing ⚠️
frb_macros/src/components/encoder.rs	0.00%	4 Missing ⚠️
frb_codegen/src/library/codegen/ir/mir/skip.rs	0.00%	1 Missing ⚠️
...ary/codegen/parser/mir/auto_accessor_parser/mod.rs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2018      +/-   ##
==========================================
- Coverage   98.32%   97.85%   -0.48%     
==========================================
  Files         410      414       +4     
  Lines       16801    16874      +73     
==========================================
- Hits        16520    16512       -8     
- Misses        281      362      +81     

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