"Drop entire stack" cannot be bound separately from "drop one item"

Closely relates to MC-203401 and MC-256811. Also relates to MC-122645, MC-147718, MC-226124 and MC-226655.

The bug

The action for dropping every single item inside of a slot is hardcoded to always use the same key as dropping only a single item. This can cause several issues: for example, if your drop key is B, then dropping all items will trigger the narrator as well (MC-122645), which is something I personally can attest to being extremely annoying.

How to fix

A separate keybind could be implemented for dropping every item. By default, it could still be Q, but could be bound to a separate key such that pressing it would drop every item instead.