fix performance regression on qs_new_tiles

1. Use StateFlow for tile states instead of SharedFlow
2. Remove StateFlow from QRCodeScannerTileDataInteractor
3. Run tile mapper's map() on UIBackground thread

Bug: 343622531
Test: atest OpenQqsThenOpenQsThenCloseFromBottom
Test: atest QSTileViewModelTest QSTileViewModelImplTest
QSTileViewModelUserInput Test
Test: atest QRCodeScannerTileDataInteractorTest
Flag: com.android.systemui.qs_new_tiles

Change-Id: Ibbf788820c02a35151eda8bb0ed1c8ec0527e0b8