Warn by default

[mateoatr]

Log warnings and errors regardless of the --verbose option.

Dependent upon dotnet/runtime#39133.

[vitek-karas]

Can you please add tests validating the behavior of the various messages? It might need some infra work though.

[sbomer]

LGTM if you add a test for the default behavior

[sbomer]

@layomia added bulk suppressions for warnings in runtime (dotnet/runtime#40106), so I think this is unblocked.

[sbomer]

For testing, maybe it would be enough to remove --verbose from the default test options: https://github.com/mono/linker/blob/7c9b806037e88df7eb40a8151808730133676668/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadaProvider.cs#L90 and add it explicitly for any tests that check informational messages?

[mateoatr]

For testing, maybe it would be enough to remove --verbose from the default test options:

https://github.com/mono/linker/blob/7c9b806037e88df7eb40a8151808730133676668/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadaProvider.cs#L90

and add it explicitly for any tests that check informational messages?

Yes, I think this should be enough, although I think this could impact #1385. @vitek-karas should I wait until the warnings cleanup is merged?