[lldb][Windows] Use WaitForDebugEventEx if available (#196817)
This makes use of
[`WaitForDebugEventEx`](https://learn.microsoft.com/en-us/windows/win32/api/debugapi/nf-debugapi-waitfordebugeventex)
over `WaitForDebugEvent` if available (Windows 10+).
The two functions are identical except for the handling of
`OutputDebugStringW`. The `-Ex` version forwards the string as Unicode
whereas the other version forwards ASCII strings. Since we don't handle
these outputs yet, it shouldn't make any difference.
Split from #196395.