Recommit "[SelectOpti][5/5] Optimize select-to-branch transformation"

Use container::size_type directly to avoid type mismatch causing build failures in Windows.

Original commit message:
This patch optimizes the transformation of selects to a branch when the heuristics deemed it profitable.
It aggressively sinks eligible instructions to the newly created true/false blocks to prevent their
execution on the common path and interleaves dependence slices to maximize ILP.

Depends on D120232

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D120233