[llvm] [DLCov 1/5] Add CMake option to enable enhanced line number coverage tracking (PR #107278)

[Djordje Todorovic via llvm-commits]

djtodoro wrote:

@SLTozer Thanks a lot for this! Very interesting.

I will review the implementation, but I am curious whether we only modified the metadata/`DebugLoc`. To be more precise, my main concern is memory usage increase, and whether we have affected `llvm::Instruction` in any way other than metadata.

https://github.com/llvm/llvm-project/pull/107278