calendar-row: Rename calendar-combo-row-item to calendar-row

Currently, the quick add popover implements its own row
widget for each calendar, which duplicates tons of unnecessary
code. This commit streamlines the calendar-combo-row-item row
widget to make it reusable elsewhere.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/362>

src/gui/common/gcal-calendar-row.blp

@@ -0,0 +1,27 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GcalCalendarRow: Adw.PreferencesRow {
+  child: Box {
+    orientation: horizontal;
+    spacing: 6;
+
+    Image color_image {
+      styles [
+        "calendar-color-image",
+      ]
+    }
+
+    Label title_label {
+      ellipsize: end;
+      xalign: 0.0;
+      label: bind template.title;
+    }
+
+    Image visibility_image {
+      halign: end;
+      hexpand: true;
+      icon-name: "eye-not-looking-symbolic";
+    }
+  };
+}