Add unit tests for the UpdateSource

Add unit tests to the OriginalUnseenKeyguardCoordinatorTest to test the
onEntryUpdated method by different sources. A seen notification should
only be marked as unseen if it's updated by the App, not the
SystemServer or SystemUi.

Fix: 399173134
Test: OriginalUnseenKeyguardCoordinatorTest
Flag: TEST_ONLY
Change-Id: I2214985d0fdad58263c1cf69278c7e9d6d54e01a