[LE boradcast] save the data into ContentProvider

The settings and systemUI use the LocalBluetoothLeBroadcast and
they use different sharedPreferences since the context is different.
It causes the data are not consistent.

Solution: Add data into ContentProvider, and listen the data changed
by the ContentObserver.

Bug: 243107842
Test: build pass. manual test in local.
atest SettingsBackupTest
atest SettingsValidatorsTest

Change-Id: I5f8367f3eb8e2dafa2986004dd8540de41409192