[llvm] Add executed MC/DC TestVectors to `llvm-cov export` (PR #105511)

[Alan Phipps via llvm-commits]

evodius96 wrote:

Thank you for implementing this! I wasn't aware of the outstanding issue and PR.  Exporting to JSON was not an immediate need, so I appreciate the engagement in supporting the JSON more fully for MC/DC.  I agree it makes sense right now to focus on executed test vectors.  I will review this within the next few days.

https://github.com/llvm/llvm-project/pull/105511