[llvm][ctx_profile] Add the `llvm.instrprof.callsite` intrinsic (#89939)

Add the callsite intrinsic. 

Structurally, it is very similar to the counter intrinsics, hence the inheritance relationship. We can probably rename `InstrProfCntrInstBase` to `InstrProfIndexedBase` later - because the "counting" aspect is really left to derived types of `InstrProfCntrInstBase`, and it only concerns itself with the index aspect (which is what we care about for `callsite`, too)

(Tracking Issue: #89287, RFC referenced there)