.github/workflows: publish test results for failed job
.github/workflows: publish test results for failed job

The GitHub Actions Linux Testing only reports limited information (can not see full stacktrace, time consumed, or stderr from child threads) when unit tests fail. Adding a step to upload the test report to Artifacts if the test fails. If the test is successful, no artifacts will be uploaded.
stanley-cheung/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,grpc/grpc-java,ejona86/grpc-java,grpc/grpc-java,stanley-cheung/grpc-java,ejona86/grpc-java,ejona86/grpc-java,ejona86/grpc-java