What does this PR do?

This PR enables the internal api used to get the global code coverage value on Test Impact Analysis scenario to a normal code coverage scenario.

Motivation

This Go testing.Coverage() api is returning a different percentage from the one reported in the stdout. This issue started when the new code coverage algorithm started to be the default algorithm.

See: golang/go#62212

Example:

--- PASS: TestValue (0.00s)
PASS
coverage: 100.0% of statements
testing.Coverage() 25
....
2025/05/22 15:23:38 Datadog Tracer v2.1.0-dev.2 DEBUG: civisibility: done.
ok      awesomeProject10/package1       1.092s  coverage: 100.0% of statements

By switching to our internal api (the internal api uses the same mechanism as the stdout format)

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.
• New code is free of linting errors. You can check this by running golangci-lint run locally.
• 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.

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