Use setIdentifier instead of dynamic categories

Change I27987301ebf393de6f781b17ed7bc789789c01ab introduced the usage of
dynamic categories to prevent the pending intent from being cached. This
is incompatible with the new T explicit intent filter enforcement, as a
dynamic category can never match any intent-filter.

Switch to use the PendingIntent#setIdentifier API introduced in API 29,
specifically designed for this use case.

Bug: 249043995
Test: m + manual
Change-Id: I2bbe4e554ef337299138f2a7691eeffc60e18e9d
(cherry picked from commit 8afc387e)
Merged-In: I2bbe4e554ef337299138f2a7691eeffc60e18e9d