Left/Right in a process tree should collapse/expand the tree branches

[nyurik]

Checklist

• I've looked through the documentation and existing open issues for this feature/feature request.

Describe the feature request

Many tree viewers have a convention of opening/closing tree branches when the user hits left/right arrow keys. Please add for consistency. Thanks!

[ClementTsang]

Hm, I was originally planning on defaulting left/right in the process widget to deal with #433.

[nyurik]

I did a first pass of implementing it in #1306 -- I think toggle on + and - is a bit confusing too, so I changed it as well.

The horizontal scrolling might be good, just probably not as common for the tree view? Perhaps ctrl+left/right?

[ClementTsang]

Closing this in favour of #454 which is more general.

[nyurik]

@ClementTsang thanks for implementing the custom bindings, but please consider convention over configuration (common in Rust) -- which is the most obvious tree behavior?

[ClementTsang]

Honestly, the first tool I think of with trees and processes that is similar to this use case is htop... which doesn't do what you describe either, as far as I'm aware, hence why I was not really on board at first.

That said yes, I can consider it, as I'm aware many other programs do act like this after playing around with a few, and I'll consider adding it as a default keybinding.