Remove old unused code

[Mikah-Kainen]

Artem

Copied from https://github.com/michaelborkowski/lh-array-sort/issues/42.

Ideas so far:

• prof/
• DpsMerge.hs should be fully subsumed by (more reasonably named) DpsMergeParSeqFallback.hs
• the "non-4" versions of mergesort code: DpsMergeSort(Par).hs (we only benchmark DpsMergeSort4(Par).hs)
• dependency on criterion-external turned out not useful and can be removed
• becnhrunner/Benchrunner_old.hs
• mutable-arrays (we use prim-mutable-arrays)