Create thread to dump shutdown check points to file

Create new method ShutdownCheckPoints#createDumpThread that
creates a thread that calls ShutdownCheckPoints#dump on a local file and
also limits the total number of files created by deleting the oldest
ones.

Bug: 113147108
Test: atest FrameworksServicesTests:ShutdownCheckPointsTest
Change-Id: I62c8eedba2ff4c10ad66636c57de07fd1370c116