SF: Split processHotplug

The disconnect case doesn't share much with the connect/reconnect cases,
and splitting the two foreshadows the hook points to register/unregister
the display with DisplayModeController.

Bug: 241285876
Test: presubmit
Change-Id: I0546ab0e8d2e709f6528adcbd9e9bf3a1e16980a
2 files changed