[Frontend] Disallow non-MSVC exception models for windows-msvc targets

The windows-msvc target is used for MSVC ABI compatibility, including
the exceptions model. It doesn't make sense to pair a windows-msvc
target with a non-MSVC exception model. This would previously cause an
assertion failure; explicitly error out for it in the frontend instead.
This also allows us to reduce the matrix of target/exception models a
bit (see the modified tests), and we can possibly simplify some of the
personality code in a follow-up.

Differential Revision: https://reviews.llvm.org/D47853

llvm-svn: 334243