## Summary of the Pull Request
This pull request ports #5096 to WpfTerminalControl, bringing it in line with the selection mechanics in Terminal. It also introduces double- and triple-click selection and makes sure we clear the selection when we resize.
Please read #5096 for more details.
## Detailed Description of the Pull Request / Additional comments
This code is, largely, copy-and-pasted from TermControl with some updates to use `std::chrono` and `til::point`. I love `til::point`. A lot.
## Validation Steps Performed
Lots of manual selection.