[JumpThreading][NFC][CompileTime] Do not recompute BPI/BFI analyzes

They can already be available, and even if not, DT/LI can be available.
We should not recompute them. Old PM is unchanged because it would
require changing dependencies, and we don't care enough about it.

Differential Revision: https://reviews.llvm.org/D124439
Reviewed By: nikic, aeubanks