Convert matrices to float in eigen

[jishnub]

After this, the following works:

julia> A = SMatrix{3,3}(1:9); # integer matrix

julia> eigen(Hermitian(A))
Eigen{Float64, Float64, SMatrix{3, 3, Float64, 9}, SVector{3, Float64}}
values:
3-element SVector{3, Float64} with indices SOneTo(3):
 -3.1574678406080774
 -0.6727679548987636
 18.830235795506848
vectors:
3×3 SMatrix{3, 3, Float64, 9} with indices SOneTo(3)×SOneTo(3):
 -0.802389   0.434025  -0.409627
 -0.168127  -0.822962  -0.542649
  0.57263    0.366546  -0.733307