AIP-203: field-behavior-required should not produce findings for common types

[noahdietz]

A few AIP-213 common types are used in requests for disparate APIs, like google.iam.v1.GetIamPolicyRequest. The dependent API cannot apply field_behavior annotations to that proto, so they should not be shown findings for this rule for those types.

Note that this should still be raised when the common types are the input/target file, just not when it is the request type of a dependent API.

This was raised in #1502.

[noahdietz]

cc @loeffel-io

[noahdietz]

Interestingly there is logic to account for this, and tests, but it is not working. I just reproduced this with a unit test using IAM and it was not ignored as being in a different package.

api-linter/rules/aip0203/field_behavior_required.go

Lines 71 to 74 in f0b7895

	if mt := f.GetMessageType(); mt != nil && !mt.IsMapEntry() && mt.GetFile().GetPackage() == pkg {
	ps = append(ps, problems(mt, pkg, visited)...)
	}
	}

[noahdietz]

The bug is that it only does this package comparison check to after the first pass of field behavior checks before deciding to recurse deeper.