Morgan Stanley is usually at the forefront of whisking young tech companies public — handling stock offerings for Apple, Google and Facebook. Now its bankers are finding it’s also lucrative to slow-walk a unicorn into the light of day. After a decade vying with Wall Street rivals, Morgan Stanley is emerging as the adviser of choice for Palantir Technologies, Peter Thiel’s secretive data-mining and visualization venture. The bank has earned about $60 million in fees arranging private funding for the 14-year-old company.