Store original values of replaced settings in Settings.Secure

Bug: 153940088
Test: atest SettingsProviderTest:SettingsHelperTest

Writing new settings to Settings.System is only available to privileged
callers. Move the storage of the original values of replaced settings to
Settings.Secure. See the attached bug for more context on replaced
settings.

Change-Id: I8f1e8e88da4766b5fca9362cdbe88d93b964db9b
1 file changed