Add missing methods for UniformScaling (#53949)
The methods `float`, `cis`, `sincos` and `sincosd` are defined for
matrices, so it makes sense for these to be defined for a
`UniformScaling` as well.
E.g.:
```julia
julia> float(2I)
UniformScaling{Float64}
2.0*I
julia> sincos(2I)
(UniformScaling{Float64}(0.9092974268256817), UniformScaling{Float64}(-0.4161468365471424))
```
