[NFC][IndirectCallProm] Refactor function-based conditional devirtualization...

[NFC][IndirectCallProm] Refactor function-based conditional devirtualization and indirect call value profile update into one helper function (#80762)

* The motivation is to move indirect callee profile update inside the
function-based speculative indirect-call promotion, so that there are
fewer diffs the vtable-based transformation and profile update is
implemented in a follow-up patch.
* The Parent patch is https://github.com/llvm/llvm-project/pull/79381