Move RingtoneTest to media/tests/ringtone

Move ringtone tests to media/tests/ringtone module that maps to run on
presubmit on any code changes on *Ringtone*.java files.

Split the tests into Ringtone general ones, relying on
RingtoneManager.getRingtone for instantiation, and new API tests in
RingtoneBuilderTest, covering the new sound+vibration features.

Fix: 304497672
Test: atest com.android.media.RingtoneTest
      atest com.android.media.RingtoneBuilderTest
Change-Id: Idcaf8851252d1dba1bc89fa8639b7d9cde27d281