Refactor: Remove TaskThumbnailViewModel and introduce TaskViewModel

- Remove TaskThumbnailViewModel and replace it with TaskViewModel
- Introduce TaskUiStateMapper class to map between TaskData and TaskThumbnailUiState
- Improve TaskView by introducing TaskViewModel and delegate to TaskContainer to show changes
- Refactor TaskThumbnailView to simplify its responsability and be able to receive TaskThumbnailUiState.
- Add TaskViewModel test and TaskUiStateMapper tests

Bug: 390583187
Doc: go/launcher-overview-unified-taskviewmodel
Flag: com.android.launcher3.enable_refactor_task_thumbnail
Test: OverviewImageTests
Test: TaskViewModelTest
Test: TaskUiStateMapperTest
Test: TaskThumbnailViewModelImplTest
Test: TaskThumbnailViewScreenshotTest
Change-Id: I90bb08d377d7a24ca803c552e0cf3897c8888b76