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
Change-Id: I542be7f798b16227614f0467259015f856720d14