* Add Benchmark for AddSingularBatch

* update compressor configs ; address PR comments

* Add b.N

* Export RandomSingularBatch through batch_test_util.go

* measure only the final batch ; other organizational improvements

* Add Benchmark for ToRawSpanBatch

* update tests

* minor fixup

* Add Benchmark for adding *All* Span Batches

* comment fixups

* narrow tests to only test span batches that won't exceed RLP limit

* address pr comments