Recommit "[TTI] Unify FavorPostInc and FavorBackedgeIndex into getPreferredAddressingMode"

This reverts commit effc3b079927a6dd3084b4ff712ec07f926366f0, with the build
problem fixed.

GitOrigin-RevId: 357237e93ec1c75302bf11975cfadc8fc2220a55
8 files changed