Add option to limit raise-together to current display

[timheide]

Summary

Adds a new preference "Limit to current display" under "Raise tiled windows together". When enabled, raising one tiled window only brings tiled windows on the same monitor to the foreground, instead of all tiled windows across the entire workspace.

Motivation / Problem

I work with multiple monitors and treat each display as a separate, independent workspace. Each monitor has its own layout and its own set of windows, and mentally I don't group windows across displays. For me they belong to different "units" of work.

With the current "Raise tiled windows together" behavior, clicking a tiled window on one monitor raises all tiled windows on the current workspace, including those on other monitors. On GNOME Shell, workspaces span all displays, so this effectively restores a kind of global layout across every monitor at once.

That feels confusing in practice: windows that have no meaningful relationship to each other (because they live on different displays) are raised together, which breaks the mental model of monitors as separate work areas.

Solution

This PR adds an optional sub-setting that scopes raise-together to the current display only where the window being raised is located. Tiled windows on other monitors are left as they are.

The original behavior is unchanged by default (raise-together-current-monitor-only defaults to false), so existing users keep the current all-monitors behavior unless they explicitly opt in.

Behavior

Raise together	Limit to current display	Result
Off	(ignored)	No group raising
On	Off	All tiled windows on the workspace are raised (existing behavior)
On	On	Only tiled windows on the same monitor as the raised window are raised

Testing

I Tested on GNOME Shell 46 (Wayland) with three active monitors
Raise together on + limit on: only tiled windows on the same display are raised
Raise together on + limit off: all tiled windows are raised (unchanged default behavior)
Raise together off: sub-switch is disabled; windows raise independently