Documentation on how to get c++ toolchain to work with bazel converage

### Page link:

https://bazel.build/docs/cc-toolchain-config-reference

### Problem description (include actual vs expected text, if applicable):

As pointed out in https://github.com/bazelbuild/bazel/issues/19353#issuecomment-1908968337, Our documentation for c++ toolchain lacks instruction on how to make it work with `bazel coverage`.

### Where do you see this issue? (include link to specific section of the page, if applicable)

_No response_

### Any other information you'd like to share?

_No response_

Start with the C++ toolchain configuration reference at https://bazel.build/docs/cc-toolchain-config-reference and read the guidance in issue 19353's linked comment. Document how a C++ toolchain should be configured for bazel coverage; the work is done when users can follow the page to enable coverage without needing separate issue discussion.

Written by the indexing model from the issue text.