gocql tracing

[mmcshane]

What changed? Add gocql tracing.

Why? Useful know when and what queries are being issued.

How did you test it? New unit tests.

Potential risks Storage latency? But this is specifically constructed so that if tracing is disabled (the default case), overhead is minimal.

Is hotfix candidate? No.

[mmcshane]

Note that there's a fair amount of threading TracerProviders into place here. The main contribution is in gocql/tracing.go and its associated unit test.

We prefer this implementation to the one in otel-contrib because this one logs gocql batch queries.