Create TAPL test suite for splitscreen

This patch creates a new file, TaplTestsSplitscreen.java, containing one TAPL test sequence.

testSplitAppFromHomeWithItself() tests the user flow of splitting from home using an app that is already running, and then selecting the app itself again as a split target from the Taskbar. The expected result is that Launcher shows an error message gracefully and does not crash.

Fixes: 267554450
Test: Ran test file locally and verified that it passes.
Change-Id: I98a1e3a4143d10a6572175711059b3a77aa5dcd0