Adding timer instrumentation for BatchSplitter and RollupTypeCacher

https://jira.rax.io/browse/CMD-355

* Added instrumentation for BatchSplitter and RollupTypeCacher ingestion processors
* Check if any other processors need that instrumentation 
* Check if any tests need to be added
I think this would be simpler if all the instrumentation were in `record()` and there is only a single timer.