[BPI] Look-up tables for non-loop branches. NFC.

This adds and uses look-up tables for non-loop branch probabilities, which have
have probabilities directly encoded into the tables for the different condition
codes. Compared to having this logic inlined in different functions, as it used
to be the case, I think this is compacter and thus also easier to check/cross
reference. This also adds a test for pointer heuristics that was missing.

Differential Revision: https://reviews.llvm.org/D114009