window: Rework properties adaptivity

Ports the sidebar to AdwOverlaySplitView, and uses AdwMultiLayoutView
to use a box at narrow sizes. A bottom sheet also
overlays the content when the window is both narrow and short.

data/resources/style-hc.css

@@ -1,3 +1,7 @@
 row.property label.title {
   opacity: 0.9;
 }
+
+.properties-border {
+  color: var(--headerbar-border-color);
+}

data/resources/style.css

@@ -57,4 +57,8 @@ dropdown.flat button:not(:hover) {
 dialog.error-details textview {
   background: none;
   color: inherit;
-}
+}
+
+.mobile-properties {
+  box-shadow: 0 -1px var(--headerbar-darker-shade-color);
+}