SF: Refactor setter for DM and override policy

Move DisplayDevice::setRefreshRatePolicy to RefreshRateConfigs, and
merge the repetitive set{DisplayManager,Override}Policy helpers.

Improve type correctness of the parameters and return value.

Bug: 241285191
Test: libsurfaceflinger_unittest
Change-Id: Iee87316e5702282b828bc3f28cd7d30041030ed5
8 files changed