Re-land "[WinEH] Add an EH registration and state insertion pass for 32-bit x86"

This reverts commit r236360.

This change exposed a bug in WinEHPrepare by opting win32 code into EH
preparation. We already knew that WinEHPrepare has bugs, and is the
status quo for x64, so I don't think that's a reason to hold off on this
change. I disabled exceptions in the sanitizer tests in r236505 and an
earlier revision.

llvm-svn: 236508