Remove length from Stateful Iterators

[wkearn]

CI is failing on nightly because of this change: JuliaLang/julia#51747

DiskArrays calls length on a Stateful iterator here:

DiskArrays.jl/src/iterator.jl

Lines 40 to 60 in 3689544

	@noinline function _iterate_disk(
	a::AbstractArray{T}, i::I
	) where {T,I<:Tuple{A,B,C}} where {A,B,C}
	datacur::A, bi::B, bstate::C = i
	(chunkiter, innerinds) = bstate
	cistateold = length(chunkiter)
	biter = iterate(bi, bstate)
	if biter === nothing
	return nothing
	else
	innernow, bstatenew = biter
	(chunkiter, innerinds) = bstatenew
	if length(chunkiter) !== cistateold
	curchunk = innerinds.itr.indices
	datacur = OffsetArray(a[curchunk...], innerinds.itr)
	return datacur[innernow]::T, (datacur, bi, bstatenew)::I
	else
	return datacur[innernow]::T, (datacur, bi, bstatenew)::I
	end
	end
	end

[rafaqz]

Surely this is a breaking change to julia Base?

[rafaqz]

@meggart we may need to define our own DiskStateful iterator and define length on it as in this case we know it is correct.

[felixcremer]

This is closed by #145 .