show(::MersenneTwister) : use module qualification (JuliaLang#40583)

show(::MersenneTwister) : use module qualification

Instead of always printing `MersenneTwister(...)`, we also prepend
`Random.` when not is scope, e.g.
```julia
julia> import Random; Random.MersenneTwister(0)
Random.MersenneTwister(0)
```

stdlib/Random/src/RNGs.jl

@@ -181,9 +181,9 @@ function show(io::IO, rng::MersenneTwister)
  seed = from_seed(rng.seed)
  seed_str = seed <= typemax(Int) ? string(seed) : "0x" * string(seed, base=16) # DWIM
  if rng.adv_jump == 0 && rng.adv == 0
- return print(io, "MersenneTwister($seed_str)")
+ return print(io, MersenneTwister, "(", seed_str, ")")
  end
- print(io, "MersenneTwister($seed_str, (")
+ print(io, MersenneTwister, "(", seed_str, ", (")
  # state
  adv = Integer[rng.adv_jump, rng.adv]
  if rng.adv_vals != -1 || rng.adv_ints != -1