OPP: Fix failing OPP Activity tests

In some devices, OPP is disabled, which makes some OPP activities
are disabled accordingly.

This CL skips those Activity tests if OPP is not enabled.

Bug: 325674236
Test: atest BluetoothOppBtEnableActivityTest \
            BluetoothOppBtEnablingActivityTest \
	    BluetoothOppLauncherActivityTest \
	    BluetoothOppReceiverTest
Flag: EXEMPT, test-only change
Change-Id: Ic7c24eae7a39ee3d1aa89ab918ffac5cf7908a6b