Split DisplayTopologyCoordinatorTest#addAndRemoveNonDefaultDisplay_

This CL is a followup CL of ag/33101767
This CLs splits addAndRemoveNonDefaultDisplay_ tests into
addNonDefaultDisplay_ and removeNonDefaultDisplay_ test cases
separately.

Bug: 407512389
Test: DisplayTopologyCoordinatorTest
Flag: com.android.server.display.feature.flags.enable_default_display_in_topology_switch
Change-Id: I0e046b3693a49c904407cec38c80e61f47960175