DO NOT MERGE Add scan background mode to Settings.Global.

This enables us to mess with the different scan intervals and shift
clients to a different scan mode in the background based on what scan
interval values we choose for the different power modes.

Bug: 71765044
Test: None. Just adding a key.
Change-Id: Id48ebc521dd3fe8a68c9c4c0bdb1018ea5b3743e
2 files changed