Allow No Sensor to be Specified in DDC

Adding the following:
<proxSensor/>

to the DDC, will stop any fallback from being used, and allow the usage
of no sensor to be used for that display. This is useful for when a
display has no sensor and the fallback should not be used. If this is
not added to the ddc, the fallback will still only occur if the display
is the default display.

Bug: 202604469
Test: dumpsys display | grep mProximitySensor
Test: com.android.server.display
Change-Id: I018b334a443f6b9a36aaeca70c673bac86446402
Merged-In: I8508a191b7c7c5990929e4d020ffd144c7faeef7