Adding @Perfect-Pixel. Welcome!
Manage StoreAccess inside GraphStoreFixture.

o Failure to close StoreAccess before deleting underlying files
  was causing test failiures on Windows.
o Also, replaced file-based string logger with StringLogger.SYSTEM
  for non-production cases, since this implementation doesn't need
  to be closed, and it would hard to manage the lifecycle of a
  logger that does need to be closed.
Remove assertion relying on messages.log to detect recovery.
Increases priority of configuration getter thread in cluster tests

Adds optional priority argument in NamedThreadFactory constructor
Uses that to have the configuration getter thread in ClusterMockTest run with highest prio
This is necessary for windows tests to pass on CI