Add WCT API for excluding individual tasks from recents.

Introduces a new WindowContainerTransaction (WCT) API,
setTaskForceExcludedFromRecents(), which allows clients to explicitly
exclude individual tasks from the Recents list. This provides a more
direct and flexible way to control task visibility in Recents.

Bug: 404726350
Flag: com.android.window.flags.exclude_task_from_recents
Test: atest WmTests:WindowContainerTransactionTests
Test: atest WmTests:WindowOrganizerTests
Change-Id: Id561740dc225860905ffc28524db083633b4685b