Update clock burn-in so it doesn't clash with udpfs

* update the UDFPS icon burn-in parameters to be in pixels
because we don't want display density to increase the
position movement
* when the clock is centered aligned, we want to make sure
it doesn't overlap with the udfps icon

Test: atest SystemUITests, manually update clock times with
with DozeUi.BURN_IN_TESTING_ENABLED enabled and see clock
doesn't interfere with the UDFPS icon.
Fixes: 192423460

Change-Id: I6f95fe3ad763971b804129b517f4c98192ab3674