[GUI] Allow other keybinds to confirm text fields

[xcape]

Currently, Enter is the only key that confirms a text field entry and closes the window (Tab, Alt+E, and Ctrl+E do not work). That becomes misleading because the tooltip says "Confirm (Tab)", but if text is selected anywhere, it doesn't work.

On more testing, it seems that Enter is just hardcoded for this purpose, which is unfortunate.

When configuring hundreds of entities, request slots, or combinator settings, reaching for Enter forces you to constantly move your right hand off the mouse. Adding support for Tab or other single-hand shortcuts to confirm and close the window would let players paste values and confirm entirely with their left hand.