Now that RemoteAction supports PendingIntent, we should be using it
instead of rolling our own fields. Continue offering legacy
constructor for some existing unit tests.
Create a notification channel for each remote app that throws at a
client app. All apps targeting O must now use channels, which give
the user better control over notifications.
Mention in docs that strings should be localized.
Test: builds
Bug: 33749182, 35012253, 34676491
Change-Id: Ic57e32025bc6caf784d3746d9f97f6595b0edb69
72ec448307