Cynthia Littleton Business EditorDavid Thewlis has signed on to star opposite Olivia Colman in “Landscapers,” HBO’s four-episode limited series from Sky Studios about a seemingly ordinary couple who become the focus of an investigation when dead bodies turn up in their yard.Will Sharpe, who worked with Colman in the offbeat 2016 British comedy series “Flowers,” has signed on to direct all four episodes.