[BUG] incorrect matrix type casting in concatenation

[GiggleLiu]

This is a bug in nightly, which breaks multiple tests.

julia> using SparseArrays

julia> ds = rand(ComplexF64, 4, 4);

julia> sp = sprand(ComplexF64, 4, 4, 0.5);

julia> vs = [sp, ds];

julia> typeof.(vs)
2-element Vector{DataType}:
 Matrix{ComplexF64} (alias for Array{Complex{Float64}, 2})
 Matrix{ComplexF64} (alias for Array{Complex{Float64}, 2})

In Julia1.7, it does not cast a sparse matrix to a dense matrix.

[fredrikekre]

See #44096 and in particular discussion in #44096 (comment). See also #43127, which is mentioned in NEWS for release 1.8. Maybe want to use the sparse_cat functions.

[fredrikekre]

Duplicate of #44821.