Core: Add test method to hooks object.

[jonnyreeves]

Provides an alias for QUnit.test to allow a more natural, nested nested api; this allows the author to write their tests as follows:

QUnit.module('action/example', t => {
    t.beforeEach(/* ... */);
    t.test('it should be awesome', assert => {
        assert.ok(true, 'rock and roll!');
    }
})

The downside I can see to this change is that it moves the existing convention away from the t / hooks argument being solely based around adding module hooks, however I feel there is a real benefit from not having to constantly write QUnit everywhere 😁

Thanks!

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[jonnyreeves]

Ah sorry, you are already discussing this feature in #978. Thanks again for your hard work on this awesome library.

[leobalter]

thank you, @jonnyreeves!

Hooking the test on the callback arguments is the easiest part, the complexity comes registering the children tests as part of their parents. That's the biggest challenge at #978, I assume.