Make ViewConfigurationController public

Mockito + Dexmaker cannot mock package-private class, even with the
unit tests being in the same package.

VirtualDeviceManagerServiceTest is failing locally with:

UnsupportedOperationException: cannot proxy inaccessible class class
com.android.server.companion.virtual.ViewConfigurationController

Bug: 263231559
Test: atest
Flag: EXEMPT no-op
Change-Id: I6effd6d6f9e00d6a931479183d98b96c74ad6ab4