Situational Awareness, the hedge fund whose aggressive AI bets soured badly in July, is backed by a formidable lineup of Silicon Valley and Wall Street investors who put their faith in a 20-something founder with no prior professional investing experience.  Among the fund’s investors are Dan Sundheim, founder of the hedge fund D1 Capital Partners and a major SpaceX shareholder; Silicon Valley investor Neil Mehta, co-founder of venture-capital firm Greenoaks; the foundation of Gaurav Kapadia, founder of investment firm XN; and Feroz Dewan, the former head of public equities at Tiger Global Management, according to people familiar with the matter.…