Ensure SubscriptionPlans can be removed

Add a duration that the plans last and don't read to/write from disk
for plans. Make non-duration setSubscriptionPlans API deprecated.

Test: atest SubscriptionManagerTest, NetworkPolicyManagerServiceTest
Bug: 210696427
Change-Id: I93aece78eda324c333fbf9f1adbedcf46e4864f0
Merged-In: I93aece78eda324c333fbf9f1adbedcf46e4864f0