Fix support of Dirac and LocationScale

[devmotion]

This PR fixes the support of Dirac and LocationScale.

Currently:

julia> d = LocationScale(1//2, 1//3, Categorical([0.2, 0.8]));

julia> support(d)
1:1

julia> d = Dirac(3.4);

julia> support(d)
3:3

With this PR:

julia> d = LocationScale(1//2, 1//3, Categorical([0.2, 0.8]));

julia> support(d)
5//6:1//3:7//6

julia> d = Dirac(3.4)
Dirac{Float64}(value=3.4)

julia> support(d)
(3.4,)