[llvm] [llvm-profgen][SPGO] Support profiles with multiple concurrent processes (PR #169353)

[Snehasish Kumar via llvm-commits]

snehasish wrote:

Thanks for clarifying the PID filtering. I'm curious, what kind of specific use cases have you encountered where filtering by PID is necessary, rather than aggregating samples from all processes of a given binary?

https://github.com/llvm/llvm-project/pull/169353