Recursively check wrapper arrays for issparse

[oxinabox]

Do we want this?
I don't know.
What does it mean to be issparse?
I haven't seen a defination of an interface that must be furfilled.

Possibly all people want this for is to know if they have some algorthm that really won't run great on a sparse array, then they could issue a warning or run collect to make it dense.

issparse compiles away.

julia> @code_llvm debuginfo=:none issparse(Transpose(Base.ReshapedArray(Symmetric(m), (20, 5), ())))

define i8 @julia_issparse_2137([1 x { { { i64, i64, {}*, {}*, {}* }, i32 }, [2 x i64] }]* nocapture nonnull readonly align 8 dereferenceable(64)) {
top:
  ret i8 1
}

julia> @code_llvm debuginfo=:none issparse(Transpose(Base.ReshapedArray(Symmetric(Array(m)), (20, 5), ())))

define i8 @julia_issparse_2139([1 x { { {}*, i32 }, [2 x i64] }]* nocapture nonnull readonly align 8 dereferenceable(32)) {
top:
  ret i8 0
}

[fredrikekre]

#34308 ?

[oxinabox]

Huh, apparently i already made this PR.
Go past me.

I will forcepush this branch over to that one