Debounce on file read

[isidorn]

If a file is getting updated every 500ms and we need 1000ms to read that file we end up in a spot where we have too many file reads since they do not get canceled.
Optimally we would cancel an outdated file read if we need to read that file again.

Example program / large file can be found here #33378

fyi @alexandrudima

[alexdima]

I've just checked the window also freezes on stable, so it is not a regression caused by preserving the undo stack in this case.

I think this also causes some jumping around to happen. If I follow Isidor's steps the view/cursor jumps around all the time. I think there are some code paths that restore the view state or something.