(Reuters) -Tesla Inc boss Elon Musk said on Monday he will serve as chief executive of Twitter, the social media company he just bought for $44 billion, a move that Wall Street analysts have said could stretch the billionaire thin. Musk, who also runs rocket company SpaceX, brain-chip startup Neuralink and tunneling firm the Boring Company, fired Twitter’s previous chief, Parag Agrawal, and other top company officials last week. Tesla’s stock has lost a third of its value since Musk made an offer to buy Twitter in April, compared with a 12% decline in the benchmark S&P 500 index in the same pe…