This PR deprecates `extract_eq_drop_take` in favor of the more correct
name `extract_eq_take_drop`, so that we'll be able to use the old name
for a lemma `xs.extract start stop = (xs.take stop).drop start`. Until
the deprecation deadline has passed, this new lemma will be called
`extract_eq_drop_take'`.
This PR provides `Array` operations analogous to `List.min(?)` and
`List.max(?)`.
I had to prove a few auxiliary lemmas. Downstream in Batteries, which
already had `List.min` and `List.max`, I renamed their variants to
`List.rangeMin` and `List.rangeMax` in the PR testing branch. Their
version is more general in the sense that it has `start` and `stop`
autoParams, like `Array.foldl` has, but I think the futore belongs to
`Subarray.min` instead (which I haven't implemented yet).
