SANTA MONICA, CALIF., Feb. 13, 2000 -- A week after Leo's second coming, other big Hollywood names -- in the form of Ben Affleck, Bruce Willis, Meg Ryan and Diane Keaton -- are also coming out to play. Making their nationwide debuts in the coming week are the Wall Street flick "Boiler Room," the mobster-gone-straight comedy "The Whole Nine Yards" and the sibling-rivalry antics of "Hanging Up." Here's a rundown of what's up: FRIDAY "Boiler Room" (New Line) -- Giovanni Ribisi plays an upstart stockbroker freshly recruited for a job in a firm nicknamed the "boiler room." Ben Affleck, Vin Diesel and Nia Long co-star. (Wide release) "Hanging Up" (Sony) -- Meg Ryan, Diane Keaton and Lisa Kudrow co-star as sisters who come together to care for their dying father played by Walter Matthau. (Wide) "Pitch Black" (USA) -- In the sci-