MSIM: voice/sms subscription related API changes.

 - Add APIs to get/set the default sms subscription
 - Add APIs to get/set Voice/SMS prompt mode status

Conflicts:
telephony/java/android/telephony/SubscriptionManager.java
Change-Id: I7f06a1f45d59c617e07c1b142a11828f7cda944b

Signed-off-by: artas182x <artas182x@gmail.com>