chore(config/tracer): migrate ciVisibilityNoopTracer

[mtoffl01]

What does this PR do?

Migrates tracer to using Config.ciVisibilityNoopTracer rather than its own config.ciVisibilityNoopTracer

Motivation

datadoghq.atlassian.net/browse/APMAPI-1748

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 ./scripts/lint.sh 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.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-12-08 18:54:59

Comparing candidate commit 2b8373b in PR branch mtoff/ciVisibilityNoopTracer with baseline commit d48d8a5 in branch mtoff/ciVisibilityEnabled.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 3 metrics, 0 unstable metrics.