fix: arrayElement overloads failing with non-arithmetic iterators

[eric-bodhi]

arrayElement(start, end) overloads would fail when being used with bidrectional iterators or basically anything that wasnt a random_access_iterator, so I added overloads for both random_access_iterator's and every other form.
Since random_access supports arithmetic we can just access index, but since every other iterator doesn't support we need to hand roll to the index.

Even before I rewrote the function yesterday it still would've failed on list containers or non-random_access iterators.

[eric-bodhi]

Algo seems to be passing over range twice...

[eric-bodhi]

No, I was gonna say the algo was multi-passing and being inefficient, there's a single pass algorithm that's more elegant here.