NIU Actions: Change AppTheme to LauncherTheme

Some theme attributes used for the NIU Actions Overview were originally defined in a theme that inherited from LauncherTheme. However, 3rd-party Launchers that also used themes derived from LauncherTheme were unable to access these attributes, leading to crashes when they tried to open the Recents screen on Go devices. Just adding the attributes to LauncherTheme solves this issue.

Bug: 194810415
Test: Manual (tried a couple 3rd-party launchers on Wembley)
Test: m -j RunLauncherGoGoogleRoboTests
Change-Id: I7a2541f2a2ab3b39e0c6cf2fe40a4b096047df70