Verify ActivityStackCallback on split pairs

Verify ActivityStack when there's a SpitInfo update.
Verify standalone ActivityStack TBD.

Test: atest cts/tests/framework/base/windowmanager/jetpack/src/android/server/wm/jetpack/embedding/
Bug: 372587505
Flag: TEST_ONLY
Change-Id: Id6fc8aae3e6d8652be96922b082bdbe1950c3a6b