Read setting media show on lockscreen

It sets the current value of show media on lockscreen setting to the
boolean responsible for either showing or hiding UMO on lockscreen as
the default value once KeyguardMediaController class is created.

Bug: 259055314
Test: atest KeyguardMediaControllerTest
Change-Id: Ibf355798522f3de11b6f2f6b935a67dc615219c3