The Wall Street stalwart is betting that investors want it to be more boring. : Morgan Stanley announced yesterday that it plans to buy Eaton Vance, the investment and wealth management firm, in a $7 billion deal. Coupled with the firm’s $13 billion purchase of E-Trade earlier this year, it shows the Wall Street stalwart’s move to less flashy — but steadier — fee-based businesses, a sign of the times for the financial industry as a whole.