Add ArrayList.sort

[data-man]

No description provided.

[andrewrk]

I don't think we need helper functions in ArrayList for things that can generally be done on slices.

list.sort(std.sort.asc(i32))

vs

std.sort.sort(list.toSlice(), std.sort.asc(i32))

we don't need to have all the std.mem functions in the ArrayList namespace either.

[andrewrk]

I also removed count and the iterator API in c3d8b1f, and closed #3037 for similar reasons.

[data-man]

I also removed count and the iterator API

Yes, it's sadly.
I propose revert it, and to add more iterators to std.
E.g. reversedIterator.
It'll allow to implement a flexible library for functional programming.