Maintains fallback Wallpaper connections after set wallpaper

When setting a new wallpaper when the device is connected to multiple displays, fallback connections must be updated:
1. Remove connection: If the new wallpaper is compatible with displays that were previously incompatible.
2. Create connection: If the new wallpaper is incompatible with displays that were previously compatible.

Test: atests FrameworksMockingServicesTests:WallpaperManagerServiceTests
Flag: android.app.enable_connected_displays_wallpaper
Bug: 384520326
Change-Id: I097c1ab2ee718b6d83ed3e96fb81d0b8b0955053