the GenericMemory doc string isn't included in the docs

[nsajko]

GenericMemory is referred to in three places in the in-development docs, but not documented itself. It's public and has a doc string, though, although the doc string doesn't describe the kind and addrspace type parameters.

[nsajko]

GenericMemoryRef is likewise public and not documented, but it doesn't have a doc string, either.

[oscardssmith]

I think this was somewhat intentional. We know that regular Memory has the interface we want, but I think we wanted a release or two and a few examples using the addrspace and kind before we actually decide that the GenericMemory doesn't have any design defects that would require breaking changes if it was part of the interface.

[nsajko]

If GenericMemory or GenericMemoryRef aren't part of Julia's API, probably they:

1. shouldn't be public/exported (currently we have Base.ispublic(Core, :GenericMemory) == Base.ispublic(Core, :GenericMemoryRef) == true and they're exported into Main)

2. shouldn't be referred to from anywhere in the documentation

[LilithHafner]

@oscardssmith, would you be willing to put a note in the docstring describing what is and isn't guaranteed to remain stable?

e.g. should package authors define f(::Memory{T}) where T or f(::GenericMemory{IDK, T}) where {IDK, T}. Lacking this I think it's all going to end up semi-public upon the release of 1.11 at the very least.