Allow user to tap on stashed app to launch task in fullscreen

This patch implements a new feature that allows the user to tap on the staged app rectangle in split staging mode. When the user does so, split selection will be canceled, and the staged app will animate out to fill the screen and launch in fullscreen.

Done by creating a new onClick listener on mFirstFloatingTaskView that sets up the screen-filling animation, and then calls a new RecentsView function, launchStagedTask(), that launches mSplitHiddenTaskView and cleans up RecentsView afterwards (similar to what happens when a split pair is selected, but only one app is launched).

Open issues:
- After the staged task animates out to fill the screen, the task itself loads instantly without animating in. Ideally, it should fade in, similar to what happens when two split tasks are loaded in.

Bug: 257513449
Test: Manual on tablet
Change-Id: I2ae8e13e1c9848aae1978a536766c370949fd08b