[DeviceConfig] cherry-pick deleteProperty SystemApi

This is a cherry-pick of deleteProperty SystemApi that is already added
in internal branches.

Currently there is only a shell command to delete a property.
Adding an API to do the same.

Bug: 184001163
Bug: 226423598
Test: atest android.provider.DeviceConfigTest
Change-Id: I43d7177c509501efd65e32ab3ad000d17d6ffb6c
Merged-In: I43d7177c509501efd65e32ab3ad000d17d6ffb6c