Add Ctrl+P as shortcut to quick open files in addition to Shift+Alt+O

[kevincardona]

This also adds ED_SHORTCUT_ARRAY_AND_COMMAND which uses ED_SHORTCUT_ARRAY to allow multiple default command shortcuts.

There's no overlap with any pre-existing commands and will make the transition easier on VS Code users as it's the same shortcut.

[Calinou]

I rely on Ctrl + P a lot in VS Code, but I rarely ever use Alt + Shift + O as it's an unusual shortcut. Alt + Shift is what I associate with accidentally switching keyboard layouts on Windows 👀

[kevincardona]

It looks like the checks failed, i'm not familiar with the nuances of the linux compilation/testing and am not sure if these changes were related to the failure in the linux tests (divide by zero in Node3DEditorViewport::_update_camera). I rebased with master

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉