should dms have a toggle for setting gtk-enable-primary-paste?

### Feature Description

Recently, GNOME [(via gsettings-desktop-schemas)](https://gitlab.gnome.org/GNOME/gsettings-desktop-schemas/-/merge_requests/119) changed the default value of gtk-enable-primary-paste to false.

I just got hit with this after an update and I was wondering why middle-click wasn't working in ghostty despite using niri.
Many users may be unaware why the feature stopped working or never know this feature existed.
Gnome doesn't expose a GUI setting to set it.

I use both middle-click to paste and autoscroll and never had an issue with it conflicting.

### Use Case

This has been a feature forever and I use it every day.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

a toggle in the clipboard section of dms settings

### Alternatives/Existing Solutions

install extra software, run a terminal command or edit the ini config file

Start by locating the clipboard section of the dms settings UI and its existing configuration handling. Check how settings are persisted, then add a toggle for gtk-enable-primary-paste and verify that enabling it restores middle-click paste behavior.

Written by the indexing model from the issue text.