Show installed clock plugins in picker app.

Added methods to ClockPlugin to provide information to picker app.
Due to this change, I bumped the api number of the ClockPlugin
interface.

Bug: 125370285
Test: atest ClockManagerTest
Test: checked clock from plugin apk appears in picker app
Change-Id: I0dc3d5a450f7d352900b077b28c670ebadb874e7