backend/wayland: key event when focused with pressed keys

[emersion]

1. Start the Wayland backend
2. Focus the wlroots window with some keys pressed (e.g. in Sway, mod+arrow to focus or mod+number to switch to rootston's workspace)
3. Nested wlroots sends a key event

We need to update the internal key state without triggering a key event.

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wlroots has migrated to gitlab.freedesktop.org. This issue has been moved to:

https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/1769