Added Tests for Secondary Display Launcher

These UIAutomator tests for secondary display launcher cover app drawer, drag-n-drop functionality, app predictions, pin/unpinning icons, and correct back press behavior.

We are deviating from  go/modify-tapl due to the time constraints of this project as outlined here (https://docs.google.com/document/d/1wLb2h8qCPGur-VsufCH4mLnnuLDLcmMq0FrCo7ichu8/edit#heading=h.brf6af3bno4g).

A preliminary design document has also been created to reference for future TAPL integration (https://docs.google.com/document/d/1H642SSu5DCM_zSXTsvTWumgm3OHIxsKEXvTlTeC4y54/edit?resourcekey=0-M9sTxdyQBi8bUy5cpjmJNA#heading=h.90f2s4sc5ic9).

Before TAPL integration, we need to follow up on test rewrite to eliminate antipatterns in the following bug: b/242776943.

Bug: 241166788
Test: Run Locally, on presubmit, and on a test on a cuttlefish emulator
Change-Id: I556a47b93a7ea3b2583dbc1efd2de7623d820e2a