LogicalIndex should not be <: AbstractArray #51071
Description
Having AbstractArray around that don't define getindex is problematic for anyone extending the Array interface or dealing with array indexing.
The Julia interface documentation specifies that all arrays need size and getindex. But in practice it seems even getindex is not needed. LogicalIndex not defining getindex also makes it ok to do in the ecosystem, so packages like InvertedIndices.jl do it too.
Really, LogicalIndex is an iterable, but not an AbstractArray, and we should mark that somehow in the type.
I guess this is one for julia 2.0
(or just collect the iterator and take the performance hit)