[llvm] [GSYM] Callsites: Add data format support and loading from YAML (PR #109781)

[Kyungwoo Lee via llvm-commits]

https://github.com/kyulee-com approved this pull request.

Overall, it looks good to me. Since this is primarily for testing a new feature, I won't go into every single detail. However, I'll leave it to others, especially @clayborg, to approve this approach, too.

https://github.com/llvm/llvm-project/pull/109781