Fix: Use original icon drawable for TaskThumbnailView

- It modifies TasksRepository to return the original icon drawable directly without mutating or replacing it, ensuring the original drawable is used.
- Moved the mutate and copy of the drawable into the TTV (View layer), to prevent mutating the source of the icon for everybody else.
This commit addresses two issues:

These changes aim to fix issues with task icons that are displayed with
zoom after being modified by TTV.

Fix: 392568687
Fix: 392583703
Flag: com.android.launcher3.enable_refactor_task_thumbnail
Test: OverviewImageTest
Test: Manual
Change-Id: I29e81ba3518ecad09b96d9a5c0fa16e6931bfb39