He could have begun coasting a long time ago, through westerns or “Dirty Harry” spinoffs — the definitive, intractable loner. Or lived on in the national TV vernacular as “Rawhide’s” Rowdy Yates. But Eastwood’s lean leathery figure kept striding into new territory, middle age being the most difficult and dangerous — especially in Hollywood.Over the past decade, as actor, director or both, he’s reached deeper levels of affecting work. “Unforgiven,” “Mystic River” and “Million Dollar Baby” each in their ways are viscerally moving, and, like him, meditatively spare and artistically assured. He inherited his economic, no-nonsence approach to filmmaking from mentor Don Siegel (right) and has shown that it’s possible after all for American lives to have a second act.