Clear dream settings when package uninstalled

This change ensures we clear any component names in Settings which match
uninstalled packages.

Bug: 338210427
Test: manually on device by setting 3P screensaver and then uninstalling
the app, and checking settings value via adb
Flag: EXEMPT bugfix

Change-Id: I87d3bc30fb9e76efadf8ab751a5ed7fbe1362788