If last week was a big one for Netflix (what with “Mank” and “Hillbilly Elegy” out in theaters), then this one belongs to Amazon, who have a pair of big projects launching via their Prime Video subscription service. The first is “12 Years a Slave” director Steve McQueen’s anthology “Small Axe,” an epic and altogether unconventional series that doesn’t fit neatly into the “film” or “TV” categories: McQueen has made five features, all set in London’s immigrant West Indian community, dealing with aspects of cultural identify, racism and community. Of the three entries I’ve seen, this week’s entry, “Mangrove,” is the strongest — and a great way to kick off the cycle, with a courtroom drama for those who felt Netflix’s “The Trial of the Chicago 7” didn’t give adequate time to Bobby Seale.