Search is very allocation heavy

Started up a fresh GNOME OS (Nightly) instance on a laptop and upon entering the overview typed a couple characters and things were quite slow.

Wrote some new tooling for Sysprof to dive in a bit and see why. gnome-clocks is the offending binary but a majority of the time is in libgweather. Here is a breakdown of allocations for about 2 seconds of runtime.

Nearly 250 MB of allocations to service a couple keypresses is likely a bit higher than we would anticipate, especially since the search data is itself within mmap'able GVariant-serialized files with structures compiled with gvariant-schema-compiler.

Here is a bit of the top-offenders breakdown.

 240.2 MB : foreach_city.constprop.0
  71.5 MB : gweather_location_next_child
  68.5 MB : call_in_idle_cb
  68.0 MB : clocks_search_provider_deserialize_location
  67.9 MB : gweather_location_deserialize
  67.9 MB : gweather_location_common_deserialize
  67.9 MB : gweather_location_find_nearest_city
  66.3 MB : _dbus_clocks_search_provider_get_subsearch_result_set
  66.1 MB : clocks_search_provider_get_subsearch_result_set_co.isra.0
  61.3 MB : g_object_new
  61.2 MB : g_object_new_internal.part.0
  60.9 MB : g_object_new_with_properties
  60.9 MB : g_type_create_instance
  56.9 MB : location_ref_for_idx
  39.3 MB : clocks_search_provider_search_locations_recurse_co.isra.0
  17.4 MB : g_object_unref
  16.5 MB : g_object_notify_queue_freeze
  11.0 MB : g_data_set_internal
   7.1 MB : clocks_search_provider_search_locations_recurse
   3.8 MB : subdivide_infos
   3.2 MB : clocks_search_provider_location_matches
   2.1 MB : _dbus_clocks_search_provider_get_result_metas
   2.1 MB : clocks_search_provider_get_result_metas
   2.0 MB : g_source_new
   2.0 MB : g_idle_source_new
   1.9 MB : g_string_sized_new
   1.9 MB : g_utf8_casefold
   1.6 MB : g_string_expand
   1.3 MB : g_source_destroy_internal
   1.3 MB : g_source_callback_unref
   1.0 MB : clocks_search_provider_search_locations_co.isra.0