[clang] [llvm] [SanitizerCoverage] Add an option to gate the invocation of the tracing callbacks (PR #108328)

[Julian Lettner via cfe-commits]

https://github.com/yln approved this pull request.

LGTM, looks harmless enough.  Please ping again for review and wait a few more days before merging to give other reviewers another chance to chime in.

In the follow-up PR that expands support for this to trace-cmp, does it make sense to document this option here [SanitizerCoverage](https://clang.llvm.org/docs/SanitizerCoverage.html)?

https://github.com/llvm/llvm-project/pull/108328