Create generic implementation of PerDisplayStore.

Most of the "Store" classes for multi display, have the same
implementation.
To avoid logic duplication, this generic class can be used now instead.

Also migrates StatusBarWindowControllerStore and
StatusBarInitializerStore to use it.

Test: PerDisplayStoreImplTest
Bug: 373800041
Flag: com.android.systemui.status_bar_connected_displays
Change-Id: I49fc4207138f396ef3b5a3381270164c54e991e7