SPOILER ALERT:  This article contains spoilers for the first three episodes of “ The Testaments ,” now streaming on Hulu. Bruce Miller is plunging back into the world of Gilead — and he’s bringing an old friend with him.  Miller, the Emmy-winning creator of “The Handmaid’s Tale,” is now serving the same role with “The Testaments,” following an entirely different corner of Margaret Atwood’s theocratic universe. But, as the series’ first three episodes make clear, even though we’re not following