[ENHANCEMENT] Define an `SparseArraysBase.issparse` trait function and associated trait

[mtfishman]

Define an SparseArraysBase.issparse trait function with an associated type trait SparseArraysBase.IsSparse, in the style of SimpleTraits.jl.

We could use SparseArraysBase.issparse(a) = interface(a) isa AbstractSparseArrayInterface as a default definition.

Possibly we can overload/repurpose Base.issparse for this but I don't know how general that is meant to be, for example:

julia> using SparseArrays: issparse

julia> using LinearAlgebra: Diagonal

julia> issparse(Diagonal(randn(4)))
false