Instead of opting generated_plugin_registrant.dart out of a growing list of individual lints can we just exclude it from analysis altogether?

I imagine we could list it in the exclude section [1] of the analyss_options_user.yaml file.

It would break customers that have a custom analyzer options file with public_member_api_docs and/or lines_longer_than_80_chars enabled. They'd have to add a similar opt-out section to their options file. In the future, when we generate an analyss_options.yaml file on flutter create (see #78432) we could auto-include that.

This change would help with enabling dart-lang/sdk#35234. Currently, those generated ignores are not always ignoring a warning and hence trigger a warning that they are unused.

And it would also stop us from having to add more opt-outs to that file in the future.

[1] https://dart.dev/guides/language/analysis-options#excluding-files
[2] https://github.com/flutter/flutter/blob/master/packages/flutter/lib/analysis_options_user.yaml