[llvm] [memprof] Use CSId to construct MemProfRecord (PR #88362)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> Should we add a unit test to check that we expanded the callstack ids correctly?

I've added one.

Please take a look.  Thanks!

https://github.com/llvm/llvm-project/pull/88362