Move ProcessInfo from Host to Utility.

Move ProcessInfo from Host to Utility.

There are set of classes in Target that describe the parameters of a
process - e.g. it's PID, name, user id, and similar. However, since it
is a bare description of a process and contains no actual functionality,
there's nothing specifically that makes this appropriate for being in
Target -- it could just as well be describing a process on the host, or
some hypothetical virtual process that doesn't even exist.

To cement this, I'm moving these classes to Utility. It's possible that
we can find a better place for it in the future, but as it is neither
Host specific nor Target specific, Utility seems like the most appropriate
place for the time being.

After this there is only 2 remaining references to Target from Host,
which I'll address in a followup.

Differential Revision: https://reviews.llvm.org/D58842

llvm-svn: 355342