contrib/gocql/gocql: implement observer api based tracing

[rarguelloF]

What does this PR do?

• Adds CreateTracedSession, and NewObserver functions that make use of the gocql observer apis: (it only implements the query, batch and connect observers for now).
• Adds new options WithTraceQuery, WithTraceBatch and WithTraceConnect to enable/disable these observers individually (all are enabled by default).
• Mark the existing wrapping functions and types as deprecated.

Differences with the existing tracing method:

• The tags cassandra.paginated and cassandra.consistency_level are not set, since the required information is not available in the observer api.
• The new observer based functions set out.host to the actual host name instead of the cassandra host ID. The host ID is set to a new tag called db.cassandra.host.id.
• The new observer based functions ignore the DD_TRACE_GOCQL_COMPAT env variable introduced in [contrib/gocql] reporting both cluster and datacenter #2577 and instead directly set the correct values for the cassandra.cluster and cassandra.datacenter tags.
• cassandra.row_count is a number value instead of a string.

Motivation

Using the observer apis makes this instrumentation easier to use and maintain. It also allows to use the native gocql types instead of our custom wrapper types.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-08-12 10:12:32

Comparing candidate commit c6c0385 in PR branch rarguelloF/AIDM-229/gocql-observer-api with baseline commit 0462924 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 58 metrics, 1 unstable metrics.

[ufoot]

This is great IMO, much better than the previous API. Left a few comments in the review.

[ufoot]

^ my understanding is that this specific call will NOT trace anything.

[EDIT] me wrong, indeed by default this is true, forget about this. Maybe only comment somewhere that the default is "it's traced".

Suggested change

	session, err := gocqltrace.NewTracedSession(cluster, gocqltrace.WithServiceName("ServiceName"))
	session, err := gocqltrace.NewTracedSession(cluster, gocqltrace.WithServiceName("ServiceName"), gocqltrace.WithTraceQuery(true), gocqltrace.WithTraceBatch(true), gocqltrace.WithTraceConnect(true))

as we have to explicitly pass WithTrace<Something> to activate tracing (but I may be wrong, just asking)

[ufoot]

Thanks for addressing all my remarks, looks good!