[llvm] [Sample Profile] Check hot callsite threshold when inlining a function with a sample profile (PR #93286)

[via llvm-commits]

WenleiHe wrote:

> > inlining is guaranteed to be bounded by the inlining done in the previous build.
> 
> That's not necessarily true for subsequent builds we do modify the sample profile (merging, downsampling etc.). Using a profile that does not completely obtained from the matching binary does result in under-optimization as expected, but it should not cause a significant compile time increase.

Actually when using merged profile, long compile time is quite common. I know that both of us use the practice of merging a bunch of profiles from different top services to drive PGO of some long tail services. A merged profile make optimization less selective, which usually lead to size bloat and longer compile time. For that reason, we are moving away from that practice. 

All that said, I'm ok with this change if you can measure performance on a server workload to make sure it won't regress perf. 

https://github.com/llvm/llvm-project/pull/93286