treewide: extend stylix.imageScalingMode support

Add stylix.imageScalingMode support to all modules except:

- hyprlock
- hyprpaper
- kde
- lightdm
- sway

Closes: https://github.com/danth/stylix/issues/677
Link: https://github.com/danth/stylix/pull/678

Reviewed-by: NAHO <90870942+trueNAHO@users.noreply.github.com>
Reviewed-by: Daniel Thwaites <danth@danth.me>

modules/feh/nixos.nix

@@ -16,5 +16,18 @@
         || i3.enable
       )
     )
-    "${pkgs.feh}/bin/feh --no-fehbg --bg-scale ${config.stylix.image}";
+    (let
+      inherit (config.stylix) imageScalingMode;
+      bg-arg =
+        if imageScalingMode == "fill"
+        then "--bg-fill"
+        else if imageScalingMode == "center"
+        then "--bg-center"
+        else if imageScalingMode == "tile"
+        then "--bg-tile"
+        else if imageScalingMode == "stretch"
+        then "--bg-scale"
+        # Fit
+        else "--bg-max";
+    in "${pkgs.feh}/bin/feh --no-fehbg ${bg-arg} ${config.stylix.image}");
 }