Revert "Revert "Add TaskbarModeSwitchRule to test both transient/persistent taskbar.""

This reverts commit e7011d2b.

Reason for revert: attempt to fix test issues

- Instead of using SharedPrefs which can be flaky anyways,
  we pass along a boolean to test transient taskbar when
  we are in the test harness

Bug: 257549303
Test: TaplTestsTaskbar
Change-Id: I7c15a97363adc377f29853c1fe60b1960c77bfc3