[llvm] yaml2obj: Implement Coverage mapping format (PR #129472)

[NAKAMURA Takumi via llvm-commits]

https://github.com/chapuni commented:

Basically and generally, these definitions follow and assume knowledge of the coverage mapping file format and the internal implementation.

If there would be diversion between the file format and the internal implementation, we will follow the file format.

https://github.com/llvm/llvm-project/pull/129472