Add // ignore_for_file: type=lint comments to the top of generated files

[jakemac53]

Today there are some lints that will trigger on protobuf files (such as the 80 char limit lint). The only real solution is to disable those lints entirely for the whole project.

However, this package could add // ignore_for_file: type=lint to the top of generated files so that lints are all silenced. In general for generated code this is a good practice, to eliminate noise.

[osa1]

We should do this, but just type=lint won't be enough for now as it currently doesn't ignore all lints, see #833 (comment).