fix: Updates for latest version of google-auth #478
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The latest version of
google-authuses the IAM service accounts API to sign tokens (see googleapis/google-auth-library-python#553). We need to update our unit test mocks to be compatible with this change.At the same time I'm replacing our
_EmulatorAdminCredentialstype withAnonymousCredentialstype provided in google-auth which serves the same purpose.