Add a limit on how much data an app can acquire a lease on.

+ Allow this limit to be modified using DeviceConfig properties.
+ Support DeviceConfig.getProperties() in TestableDeviceConfig.

Bug: 144155182
Test: atest --test-mapping apex/blobstore
Test: atest services/tests/mockingservicestests/src/com/android/server/testables/TestableDeviceConfigTest.java
Test: atest services/tests/mockingservicestests/src/com/android/server/am/CachedAppOptimizerTest.java
Change-Id: I28e67a27771be04ed1d37f367abd392505adc5c4