Load tile icons while mapping state

Previously we provided code to load icon instead of actually doing the
loading in the mapper. This CL reduces thread contention among
tiles by moving the mapping to UiBackground thread. The QSTileState no
longer needs icon suppliers. Just icons.

Flag: com.android.systemui.qs_new_tiles
Fixes: 376115950
Test: atest AirplaneModeMapperTest
Test: atest AlarmTileMapperTest
Test: atest BatterySaverTileMapperTest
Test: atest FlashlightMapperTest
Test: atest FontScalingTileMapperTest
Test: atest InternetTileMapperTest
Test: atest IssueRecordingMapperTest
Test: atest LocationTileMapperTest
Test: atest OneHandedModeTileMapperTest
Test: atest QRCodeScannerTileMapperTest
Test: atest ReduceBrightColorsTileMapperTest
Test: atest RotationLockTileMapperTest
Test: atest SensorPrivacyToggleTileMapperTest
Test: atest WorkModeTileMapperTest
Change-Id: Iff35ce6687e96aff12301667a045d8e604df2199