Save deleted channels.

To discourage the pattern of deleting channels and
recreating them to get around user settings.

Behavior:
- Creating a deleted channel brings back the old channel
(with it's old settings)
- Updating a deleted channel fails
- public getChannel apis should not return deleted channels

Also align data clean up done when clearing data & uninstalling
a package

Test: runtest systemui-notification, cts, cts-verifier

Change-Id: If19c20311c978fd8d3b1cb8b234dc1e68c7356be