This patch adds support of watchpoints to the new NativeProcessWindows plugin. The same tests as in D67168 pass with these changes when the old plugin is turned off, so they will cover this functionality when the old plugin is gone.
This looks mostly fine to me. There's still a lot more copy-pasta between the three kinds of register contexts than I'd like (e.g. on linux, all of these three cases are handled by a single class), but I don't have a clear idea what to do about that at this point.
Though the std::stringstream classes are used in a couple of places, we usually try to stay away from all std::stream classes. In this case, I'd just do a llvm::formatv(...).str()