Add // coverage:ignore-file to the header of the generated files to ignore for code coverage

Currently the header of a generated file looks like:

`///
// Generated code. Do not modify.
// source: geometry.proto
//
// @dart = 2.12
// ignore_for_file: annotate_overrides,camel_case_types,unnecessary_const,non_constant_identifier_names,library_prefixes,unused_import,unused_shown_name,return_of_invalid_type,unnecessary_this,prefer_final_fields
`
It would be great if it can be extended with:
// coverage:ignore-file

so that the generated file is ignored during code coverage analysis.
Thanks

Locate the generator or template responsible for the generated Dart file header shown in the issue. Verify how the existing ignore_for_file header is assembled, then confirm that generated files include the requested coverage:ignore-file directive and that coverage tooling ignores them.

Written by the indexing model from the issue text.