This allows setting the visibility of the minimize and maximize
window control buttons. These buttons are standard on other platforms
and some users/vendors might opt to expose them.
This setting is present in GNOME Tweaks but given its popularity,
we are bringing a subset of it to GNOME Settings.
By design:
* We don't allow reordering the buttons neither moving them to the
opposite side of the window.
* We only allow toggling the visibility of "maximize" and/or
"minimize" buttons.
* The "close" button is always visible. The pre-dermined order is
always: "minimize,maximize,close".
There are prior discussions about this feature in:
- https://gitlab.gnome.org/Teams/Design/whiteboards/-/issues/87
- https://gitlab.gnome.org/GNOME/gnome-control-center/-/issues/2006
- https://discourse.gnome.org/t/titlebar-buttons/10669/32
Related: RHEL-22606
