Handles scalar * dist, dist * scalar, and dist * dist.
# S3 method for class 'dist'
x * yA simplified distribution or edist
# Scalar multiplication simplifies for normal
z <- 2 * normal(0, 1)
z # Normal(mu = 0, var = 4)
#> Normal distribution (mu = 0, var = 4)
# Product of two distributions yields an edist
w <- normal(0, 1) * exponential(1)
is_edist(w) # TRUE
#> [1] TRUE