The Christ Hospital soon will relocate hundreds of office workers to a nearby building, part of a major expansion aimed at becoming a national destination for high-end cardiac and other medical care. The move into a large vacant building is possible following the close last week of one of the region's largest development deals in years. Christ will be the building's major tenant, signaling the hospital's growing strength three years after it withdrew in a bitter battle from the regionwide Health Alliance and started rebuilding as an independent institution.