Dec 5 (Reuters) - California Governor Gavin Newsom stressed the importance of trade with Mexico and immigrant labor at a press conference near the border on Thursday, striking a contrast with President-elect Donald Trump’s threat of tariffs and mass deportations. Newsom, a Democrat, portrayed the Republican president-elect’s planned 25% tariffs on goods from Mexico and Canada as a tax on Americans who could see increased prices if the plan moves forward when Trump takes office on Jan. 20. Trump...