Moving things to Base Julia

[Tokazama]

We've been informally talking about moving stuff to Base. I figured we should actually have a record of what has been attempted and things we think are stable enough to consider.

• ArrayInterfaceCore.parent_type: Add parenttype method JuliaLang/julia#42923
• Non-mutating methods (deleteat, insert): Functional non-mutating methods. JuliaLang/julia#46453
• Static size related stuff currently all depends on either accepting Create staticint.jl JuliaLang/julia#44538 or someone figuring out a functional alternative. A lot of methods depend on it (ArrayInterface.size, ArrayInterface.length ArrayInterface.strides, ArrayInterface.offsets, and all the known_* counterparts)
• ArrayInterfaceCore.can_change_size: More specific characterization of mutable collections with can_setindex and can_change_size JuliaLang/julia#46500
• ArrayInterfaceCore.can_setindex: More specific characterization of mutable collections with can_setindex and can_change_size JuliaLang/julia#46500
• ArrayInterfaceCore.isstructured
• ArrayInterfaceCore.has_sparsestruct
• ArrayInterfaceCore.issingular

[Tokazama]

@chriselrod and @ChrisRackauckas, feel free to edit this list as you see fit. It might also be helpful to put on the record which methods you want to participate in the conversation when they do become PRs to Base.