CORE/TESTS: Introduce Memory Persistency, Add tests for persistency & flusher.
- A simple memory persistency layer is introduced which just stores everything in memory as k-v pairs in a std::map (where the ordering guarantees allow for this to behave as expected).
- Add simple tests for the Persistency Layer interface where both RocksDB and the memory persistency layer are tested.
- Add tests for flusher which expect a running QDB instance
- Introduce death style tests where some of the exit paths from persistency layer are tested; care needed to ensure that all the threads are started inside the death tests context
Signed-off-by: Abhishek Lekshmanan abhishek.lekshmanan@cern.ch