SF: setLayerCachingTexturePoolEnabled() for the pacesetter display

Currently, SurfaceFlinger enables layer caching texture pool for the
front internal display.

With this CL, the texture pool is enabled on the pacesetter display
instead. If the pacesetter designation changes from one display to
another, the old pacesetter’s pool is disabled before the new
pacesetter’s pool is enabled.

Flag: com.android.graphics.surfaceflinger.flags.pacesetter_selection
Bug: 255635821
Test: dumpsys SurfaceFlinger --planner && new setPhysicalDisplayPowerModeTest
Change-Id: Ibaf24294bc908affb7d6056040452af3118763c0