Certainly, no playwright of August Wilson’s generation — he is 57 — has proved as ubiquitous. Every one of his first eight dramas has played in New York, seven of them on Broadway, and collectively they have received nearly 2,000 productions, from amateur companies to regional theaters to London’s Royal National Theater. Mr. Wilson has won two Pulitzer Prizes, been a Pulitzer finalist four other times, and taken seven New York Drama Critics Circle Awards.” A new production of “Ma Rainey’s Black Bottom” on Broadway seems to bring his career full circle.