CI: Generate mocks and validate diff (#1215)

Benefits:
- Sometimes mock files that should have been deleted still linger around
  the repo. Deleting and re-generating the files catches those cases.
- Less script code

justfile

@@ -175,8 +175,10 @@ generate-mocks:
 
 # run to validate no mocks are missing
 validate-mocks:
-  ./scripts/validate-mocks.sh
-
+  # delete and re-generate files to check nothing is different / missing
+  find . -name 'mock_*.go' -exec rm -f {} \;
+  just generate-mocks
+  git diff --exit-code
 
 #### TESTS ####
 

resources/providers/gcplib/auth/credentials_test.go

@@ -172,8 +172,8 @@ func createServiceAccountFile(t *testing.T) *os.File {
 	return f
 }
 
-func mockGoogleAuthProvider(err error) *MockGoogleProviderAPI {
-	googleProviderAPI := &MockGoogleProviderAPI{}
+func mockGoogleAuthProvider(err error) *MockGoogleAuthProviderAPI {
+	googleProviderAPI := &MockGoogleAuthProviderAPI{}
 	on := googleProviderAPI.EXPECT().FindDefaultCredentials(mock.Anything)
 	if err == nil {
 		on.Return(