Support `normalize`

[oschulz]

We should support LinearAlgebra.normalize and LinearAlgebra.normalize!. Unfortunately, the default implementation isn't compatible with duals, because LinearAlgebra.__normalize! requires an AbstractFloat:

julia> normalize!(ForwardDiff.Dual.(rand(5), rand(5)))
ERROR: MethodError: no method matching __normalize!(::Vector{ForwardDiff.Dual{Nothing, Float64, 1}}, ::ForwardDiff.Dual{Nothing, Float64, 1})
Closest candidates are:
  __normalize!(::AbstractArray, ::AbstractFloat) at [...]/LinearAlgebra/src/generic.jl:1678

[KristofferC]

JuliaLang/julia#41045

[oschulz]

Thanks, @KristofferC !