Allow modifying minimum consumption limit.

Create separate fields for minimum and initial consumption limits so
that they can be modified independently.

Bug: 255321890
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/tare
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/tare
Test: manually change in Developer Options UI
Change-Id: I82c146a18b54a18313de590038f2f807a2310aa0