gui: Port to Blueprint

This was mostly done with `blueprint-compiler port`.

Since Blueprint doesn't know about custom templates, I had to manually change some values from strings to literals.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/567>

src/gui/calendar-management/gcal-calendar-management-dialog.blp

@@ -0,0 +1,13 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $GcalCalendarManagementDialog: Adw.Dialog {
+  title: _("Calendar Settings");
+  width-request: 360;
+  height-request: 500;
+  content-width: 500;
+
+  Adw.NavigationView navigation_view {
+    popped => $on_navigation_view_popped_cb(template) not-swapped;
+  }
+}