Add missing datatype_module method for UnionAll types

[quinnj]

No description provided.

[quinnj]

I don't think I've seen this failure before

	From worker 1:		From worker 1:	Worker 6 failed running test ranges:
Some tests did not pass: 12107327 passed, 1 failed, 0 errored, 327680 broken.ranges: Test Failed
  Expression: cmp_sn2(Tw(xw / yw), astuple(x / y)..., slopbits)
Stacktrace:
 [1] record(::Base.Test.DefaultTestSet, ::Base.Test.Fail) at ./test.jl:651
 [2] (::getfield(Main, Symbol("##40#44")))() at /usr/home/julia/worker/11rel-amd64/build/test/runtests.jl:160
 [3] cd(::getfield(Main, Symbol("##40#44")), ::String) at ./file.jl:70
 [4] include_relative(::Module, ::String) at ./loading.jl:464
 [5] include(::Module, ::String) at ./sysimg.jl:14
 [6] process_options(::Base.JLOptions) at ./client.jl:315
 [7] _start() at ./client.jl:383

Anybody have any concerns w/ this?

[StefanKarpinski]

I'm not sure what problem this is addressing or who should review it.

[quinnj]

It's just a missing method for UnionAll types, e.g., datatype_name works on both DataType and UnionAll, but datatype_module currently only works on DataType. Hence the PR.

[Keno]

That test failure is #23497 AFAIK. As for the actual change, LGTM.