Can't have describe with same value as module name

If you have a test module called Foo you can't use Foo as the string argument to describe. And, if you do, you get a misleading error message: "The test 'Foo' contains a child test of the same name. Let's rename them so we know which is which"

Sample code:

module Foo exposing (..)

import Expect exposing (Expectation)
import Test exposing (..)

suite : Test
suite =
    describe "Foo"
        [ test "t1" (\_ -> 1 + 1 |> Expect.equal 2)
        ]

This is also discussed in #493.

Reproduce the issue with the provided Elm module and describe example, then read the discussion in #493 for related context. Trace the validation that produces the duplicate-child-name error; done means a module and describe value may share the same name without the misleading error, while genuine duplicate child names remain distinguishable.