Add update network watchlist config ConfigUpdater intent action

Network watchlist config update intent needs to be in SystemAPI as
it will be used by ConfigUpdater to push watchlist config.

We also need to mark it as SystemAPI to pass cts:
intent.IntentTest#shouldNotFindUnexpectedIntents

Bug: 71635926
Bug: 63908748
Test: Able to compile
Change-Id: I3a236fa8b0bf97249b01a2ad20c5e56d18121bd4