Currently the <cloud-backup> section in android:dataExtractionRules is
ignored unless it contains rules. Instead, we should interpret it as
'everything other than cache and no-backup dirs is eligible for cloud
backup'.
Bug: 195095045
Test: 1. atest BackupEligibilityHostSideTest
2. Use a test app with empty <cloud-backup> section to manually
test:
2.1. Empty section - everything is backed up
2.2. Empty section but "disableIfNoEncryptionCapabilitites"
set to "true" - data only backed up if the transport supports
encryption.
Change-Id: Ic8066721a46bda688f9211c51a0f2497e9caf93b
21f45cd998