[llvm] [bpi] Reuse the AsmWriter's BB naming scheme (PR #73593)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

> Can you use Value::printAsOperand ?

Ah, nice! Yes. Only thing is that this will re-initialize a SlotTracker for every edge vertex, but probably this inefficiency doesn't matter for the scenario. If it does, we can address it later.

https://github.com/llvm/llvm-project/pull/73593