SF: Obey active display's RefreshRateSelector

When a display becomes active, apply its RefreshRateSelector's policy,
as it may have changed while the display was inactive.

When booting while folded, DisplayManager first sends DisplayModeSpecs
for each display, and then powers on the outer display. Before this CL,
the outer display would become the new active/leader display, but its
DisplayManagerPolicy would never be applied.

Also, remove calls during boot (or restart) that are now redundant given
that onActiveDisplayChangedLocked is called when powering on the primary
display in onInitializeDisplays.

Bug: 250421145
Test: Force 120 Hz, and reboot while folded.
Test: Apply Ifaa46027bad8ff0945db9da5c30f2f31b6c8d10c and repeat.
Change-Id: I15e0f5a280e62baf6d4e6ea2748d95342e79ac44