Fixes#7077
This follows pretty standard behavior across native or popular applications
on both platforms macOS and Linux. The basic behavior is that if you
do a mouse down event and then drag the mouse beyond the current
character, then any mouse up actions are canceled (beyond emiting the
event itself).
This fixes a specific scenario where you could do the following:
1. Click anywhere (mouse down)
2. Drag over a valid link
3. Press command/control (to activate the link)
4. Release the mouse button (mouse up)
5. The link is triggered
Now, step 3 and step 5 do not happen. Links are not even highlighted in
this scenario. This matches iTerm2 on macOS which has a similar
command-to-activate-links behavior.
6d3f97ec1e