[Windows] Add 10s timeout to some WaitForSingleObject calls

I ran the test suite yesterday and when I came back this morning the
queue_user_work_item.cc test was hung. This could be why the
sanitizer-windows buildbot keeps randomly timing out. I updated all the
usages of WaitForSingleObject involving threading events. I'm assuming
the API can reliably wait for subprocesses, which is what the majority
of call sites use it for.

While I'm at it, we can simplify some EH tests now that clang can
compile C++ EH.

llvm-svn: 261338