SF: Simplify per-display refresh rate selection

Remove verbose, single-use helper functions/types to centralize the
selection logic and merge two passes. Avoid allocation and hashing.

Fix the algorithm to not choose a refresh rate based on total score
unless it is common to all displays, and not be thrown off by equal
scores.

Bug: 241285191
Test: libsurfaceflinger_unittest
Change-Id: I355dea767c6b564a04a51476f0cc235a1fceb879