## Summary of the Pull Request
This pull request ports the VT mouse code from TermControl to WpfTerminalControl. Our WPF control is a lot closer to Win32 than to Xaml, so our mouse event handler looks _nothing_ like the one that we got from Xaml. We can pass events through almost directly, because the window message handling in the mouse input code actually came from _conhost_. It's awesome.
Neither TermControl nor conhost pass hover events through when the control isn't focused, so I wired up focus events to make sure we acted the same.
Just like Terminal and conhost, mouse events are suppressed when <kbd>Shift</kbd> is held.
## Validation Steps Performed
Tested with MC, and tested by manually engaging SGR events in an Echo terminal.
f04b7aae87
