CG: Rewrite the parsing engine relying on the Clang LibTooling

[m5imunovic]

The parser is implemented with hand-crafted patterns that might break as clang IR format is evolving. Rely on the Clang/LLVM codebase to parse out the IR relevant data. Rewrite current IR parser C++ back-end and supporting build files.

[henrirosten]

@m5imunovic : can we close this issue as not relevant?

[m5imunovic]

Closing as non-relevant.