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
There might be some debate on whether the timing should start here or inside the `call()` method. But I think this is fine.