TestClientSupportedCompressors fails if other tests register compressors

[arjan-bal]

While adding a new compressor test in #7938, it was seen that registering a new compressor during one test causes TestClientSupportedCompressors to fail. TestClientSupportedCompressors verifies the list of compressors supported by clients. If a test compressor is registered in the same test file, it shows up in the list of supported compressors, failing the test, example failure logs.

There is a deprecated WithCompressor, dial option that can be used without registering a compressor. We should find a way to ensure that tests don't influence each other in such a way.

[arjan-bal]

@easwars I wanted to make the expected changes more concrete for someone else to pick up. One approach I could think of is:

1. Add a function named something like RegisterCompressorForTest(c Codec) func() in the internal package which returns a cleanup function that can be called to unregister/revert to the original codec after the test.
2. Make the codec package set the above function in an init() method.
3. Use the RegisterCompressorForTest in tests.

Does this sound good to you?