Add a flag to enable RingtoneV2

We are replacing the existing SystemProperties flag "persist.audio.ringtone.use_v2" with a new flag "haptics_customization_ringtone_v2_enabled". This flag will be used to obscure the usage of RingtoneV2 class until it is officially released.

Bug: 293846645
Test: N/A
Change-Id: Ib92a93b845100e8183a36e3a4ca52fe8bbd0c780