Fix Bazel Coverage with C++ to work with Remote Execution

[finn-ball]

Adds missing coverage files: #13193

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[finn-ball]

@googlebot I signed it!

[oquenchil]

LGTM

[oquenchil]

Thanks a lot @finn-ball , great work!

You are the only person so far that gave feedback about this feature. If at any point you think it's good enough, please let me know and I will remove the experimental flag.

[finn-ball]

@oquenchil - Thanks for doing the initial work here. It's been a problem for a while. I would say that before you remove the experimental flags, you may want to check this out:

#13185