Implement compression interop tests

[ericgribkoff]

There are four compressed interop tests defined in interop-test-descriptions.md but not implemented for Go:

• client_compressed_unary
• client_compressed_streaming
• server_compressed_unary
• server_compressed_streaming

These should be implemented and enabled in run_interop_tests.py.

[Hrily]

Hey folks

Raised #6717 to implement client_compressed_unary test.

But I see that the probe request from the test description does not fail for go server.

So I'm not sure whether the test that I've written is doing what it's supposed to do. Would need some help here.

[arvindbr8]

Thanks for your PR @Hrily -- but this issue might be easier for someone on our team to pick up. But if you managed to get the probe test description working, please let us know. Right now our team is facing bandwidth issues for this quarter to prioritize this.