The NCAA announced Thursday that it will expand its two March Madness tournaments by eight teams each next season, a move that will drop more early-round games into the first week of the highly popular and lucrative showcase without substantially changing its overall form. The new 76-team brackets will jam eight extra games — for a total of 12 games involving 24 teams — into the front half of the first week of the men’s and the women’s tournaments, turning what’s now known as the First Four into a bigger affair. It is the first expansion of the tournaments in 15 years, when they were bumped to 68 teams each. The 12 winners will move into the main 64-team bracket that will begin, as usual, on Thursday for the men and Friday for the women. The move comes one year before Las Vegas and Allegiant Stadium will host the Final Four of the men’s event in 2028. Most of the eight new slots are expected to go to teams in the power conferences that were already commanding the lion’s share of entries in thebracket.…