There are lots of Carrier/OEM requests for tethering
notification customization. So add a new tethering notification
updater class which can let OEM customize the behavior they
wanted.
Bug: 122085773
Test: atest TetheringTests
Change-Id: I7faacde7ac84e93ea0dfe03dd33d2cc41c589225
Tethering used SystemNotificationChannels for showing
notification before. But SystemNotificationChannels is used for
system package only, tethering package is not able to use it now.
Thus, replace it with tethering own notification channel.
Bug: 122085773
Test: atest TetheringTests
Change-Id: I854a102795c19351a4137360414926c461cc604c
Migrate the resources which are only used by tethering notification
from framework/base/core/res to tethering package resource
folder.
Bug: 122085773
Bug: 139763854
Test: build pass
Change-Id: I832103090d500fd8e2e2efb9dc7151426da3f88d
Merged-In: I832103090d500fd8e2e2efb9dc7151426da3f88d