Binding Backspace related keys do not work on Windows

[Neko-Box-Coder]

Description of the problem or steps to reproduce

It seems like Windows is using OldBackspace instead of Backspace, unlike on Linux. This is very similar to #3305 where some keybindings representations work on Linux and some don't on Windows. This one is slightly different though I guess.

So if you have something like

"Alt-Backspace": "DeleteSubWordLeft"

It won't work on Windows. And there isn't any documentation regarding this AFAIK. I think the proper solution is to merge these two bindings into just Backspace and handle the difference ourselves without exposing this technicality to the users.

Specifications

Commit hash: 9face74
OS: Windows
Terminal: WezTerm

[Neko-Box-Coder]

I can create a PR later this month that solves both this and #3305 by trying different key representations when handling a key press.