Don't lose "show unused categories" in channel list when resuming

Also change the appearance of the "show unused categories" button to differentiate it from the actual categories (and match Expressive).

Finally, move ChannelListPreferenceControllerTest to Robolectric (on-device unit tests have problems with resolving resources).

Bug: 412613378
Bug: 423068870
Test: atest ChannelListPreferenceControllerTest + manual
Flag: com.android.settings.flags.notifications_remember_channel_list_state
Change-Id: I947fdca53ffb72052fd2a4de333244cc7bbd0f8f
4 files changed