Exposed getAllSubscriptionInfoList and getSubscriptionId

1. Added getAllSubscriptionInfoList for getting all the subscriptions
   from the subscription database.
2. Added getSubscriptionId for getting the active subscription id
   from the specified slot.
3. Deprecated getSubscriptionIds, which is imposible to return more
   than one subscription in today's implementation.

Fix: 261041952
Test: Manual + CTS
Merged-In: I9396f8e329ecec815d7a4aecba0d10c1a2a9c8c7
Change-Id: I9396f8e329ecec815d7a4aecba0d10c1a2a9c8c7