Do qProcessInfo-hint binary loading later in Process setup

The remote stub may give lldb hints about binaries to
be loaded, especially in a firmware type environment, and
relay those hints in the qProcessInfo response.  The
binary loading was done very early in Process setup, before
we had any threads, and this made it complicated for people
to write dSYM python scripts which need access to a thread.
Delay the binary loading until a bit later in the Process
startup.

Differential Revision: https://reviews.llvm.org/D141972
rdar://104235301