(fix) internal/civisibility: Fix test visibility on Go 1.24

[tonyredondo]

What does this PR do?

This PR fixes Test Visibility on Go 1.24

V2: (fix) internal/civisibility: Fix test visibility on Go 1.24 - v2

Motivation

Test visibility instrumentation depends on some internal Go fields. Go 1.24 came with some changes on those internals, this PR fixes that.

• This PR also fixes an existing bug we had by casting a sync.Mutex to sync.RWMutex

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.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: tony/civisibility-fix-go-1.24
Commit report: 0e8edd6
Test service: dd-trace-go

✅ 0 Failed, 5232 Passed, 73 Skipped, 2m 6.19s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-13 11:41:05

Comparing candidate commit da1804f in PR branch tony/civisibility-fix-go-1.24 with baseline commit 7125f59 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 62 metrics, 0 unstable metrics.