Add TARE enable constant.

Add a Settings constant to control the overall enabling of TARE. If
disabled, it will clean up and drop as much as possible. Set the default
value to 0/false.

Bug: 158300259
Test: look at dumpsys output after changing setting constant value
Test: atest SettingsProviderTest:SettingsBackupTest
Change-Id: I252f792444423fe5dc801125f9e7d3a0b6ed5b42