More generic `restrict` support on various arrays with offsets

[johnnychen94]

https://github.com/JuliaImages/ImageBase.jl/pull/4/files#r691967154

Ideally, we should not dispatch on array type OffsetArray in

ImageBase.jl/src/restrict.jl

Lines 137 to 143 in 9232149

	function restrict(A::OffsetArray{T,N}, dim::Integer) where {T,N}
	indsA = axes(A)
	newinds = map(UnitRange, ntuple(i->i==dim ? restrict_indices(indsA[dim]) : indsA[i], Val(N)))
	# By shifting it back to normal array, the internal for loop becomes faster because
	# it requires less indexing computation
	OffsetArray(restrict(A.parent, dim), newinds)
	end