Add back the older Ringtone implementation to allow flag control.

This CL splits the Ringtone class into RingtoneV1 and RingtoneV2, with
a switch between them. The switch is currently a system property as
the flag system for frameworks/base is still being built.

Unfortunately the old implementation didn't have test coverage.

Bug: 293846645
Test: presubmit, manual
Change-Id: I0a7fd10261e29a74ea1798f5bfbf8eddcafa1e5e