SINGAPORE (Reuters) - Singapore's long-dominant People's Action Party (PAP) lost heavily in a single-seat by-election on Saturday, a barometer of how the government is dealing with discontent in the wealthy Asian country over immigration and the high cost of living. The result in the Punggol East ward - 54.5 percent of the vote for the Workers Party and 43.7 percent for the PAP, with the rest split by two others - does not alter the balance of power in parliament, where the ruling party will still hold 80 of 87 elected seats. ...