Add a new system service for blob store management.

This change adds a bare-bones system service, implementation will follow
later.

Bug: 143559646
Test: atest cts/tests/BlobStore/src/com/android/cts/blob/BlobStoreManagerTest.java
Change-Id: I8e93a8a1e43e1afaf6c12e0b31f3334de4691dc9
4 files changed