WifiStackService: Use local constants for notification channels

The fact that we're a different APK/Apex now, we can no longer share the
notification channels created by system_server. So, stop referring to
the channel name constants.

Bug: 142092496
Test: Still able to see all the wifi related notifications (ONA, etc)
Change-Id: I1c64f372cceb284e778159e336a060a33f49a862
7 files changed
tree: 2a5114246f2b4e3b61eb02540cb5d9bf5bcb8873
  1. service/
  2. PREUPLOAD.cfg