Captured pointer for SwapChainPanel and ScrollBar separately

[carlos-zamora]

Summary of the Pull Request

• capturing the SwapChainPanel and ScrollBar separately:
  • it used to be that the root would take pointer events. So both the scroll bar AND the terminal would respond to a mouse drag on the scroll bar. Yuck!
• Renamed MouseClickHandler and MouseMovedHandler to more generic names (since they handle touch events too).

References

So, this fixes #950, but also doesn't. The reason #950 crashes is because the copy is waaaaaay too big. This will make it so that you can't make the selection that unreasonably big anymore. That said, there's still other ways to make massive copy selections so I think there's two relevant issues here:

• Bug Report: Crash on large selection #1246 Copy large selection --> crash
• Feature Request: Scroll from selection dragging out of window #1247 While selecting, dragging mouse over top/bottom border scrolls.

PR Checklist

• Closes Terminal selects lines when scrolling down the scroll bar and crashes when right clicked afterwards #950
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan.

[DHowett-MSFT]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).