The main panel was looking for a page with tag "bolt" when the panel
is actually using the "thunderbolt" tag.

Cherry-picked from
53230201

Fixes #2973

Cherry-picked from 96cf88c6

Fixes
https://gitlab.gnome.org/GNOME/gnome-control-center/-/merge_requests/2211#note_2061610

This allows launching the Accessibility panel subpages
from the command line.

See https://gitlab.gnome.org/GNOME/gnome-control-center/-/issues/2940

The Search panel providers listbox has a placeholder label that is
visible when there are no listbox items.

The placeholder label is being considered in the list of children
of the listbox while estimating whether "Moving down" is allowed for
the listbox reorder feature.

This avoids debug logging appearing in the UI via stdout when
G_MESSAGES_DEBUG is used.

Fixes #2387

Let's manually wire the row activation to the panel creation so that
we can create panels on demand.

This also makes calls to subpages directly avoid initializing the
other panels.

Fixes #2857

I'm no longer engaged enough to be a maintainer so it's best to make that clear.
Still happy to review and be involved if others need it!
This is a great project and if you want to be more involved in GNOME I'd recommend it.

Avoids the critical below at runtime
11:14:36.7796                   **[873815]:CRITICAL: cc_util_get_smart_date: assertion 'date != NULL' failed
11:14:36.7802                   **[873815]:CRITICAL: cc_util_get_smart_date: assertion 'date != NULL' failed

Which comes from the location panel passing a NULL date object.

\#0  _g_log_abort (breakpoint=1) at ../shell/cc-log.c:72
        debugger_present = 1
\#1  0x000000000045c3c4 in cc_log_write
    (log_level=10, log_domain=0x7ffff7d592eb "GLib", log_message=0x234c400 "g_date_time_difference: assertion 'begin != NULL' failed", fields=0x7fffffffd740, n_fields=4, user_data=0x0)
    at ../shell/cc-log.c:315
        log_str = 0x234b8d0
        stream = 0x7ffff5dbb4e0 <_IO_2_1_stderr_>
        can_color = 1
\#2  0x000000000045c4f5 in cc_log_handler (log_level=G_LOG_LEVEL_CRITICAL, fields=0x7fffffffd740, n_fields=4, user_data=0x0) at ../shell/cc-log.c:348
        log_domain = 0x7ffff7d592eb "GLib"
        log_message = 0x234c400 "g_date_time_difference: assertion 'begin != NULL' failed"
\#3  0x00007ffff7c9f534 in g_log_structured_array () at /lib64/libglib-2.0.so.0
\#4  0x00007ffff7ca4f57 in g_log_default_handler () at /lib64/libglib-2.0.so.0
\#5  0x00007ffff7c9be29 in g_logv () at /lib64/libglib-2.0.so.0
\#6  0x00007ffff7c9c193 in g_log () at /lib64/libglib-2.0.so.0
\#7  0x00007ffff7c787fa in g_date_time_difference () at /lib64/libglib-2.0.so.0
\#8  0x000000000059c186 in cc_util_get_smart_date (date=0x0) at ../panels/common/cc-util.c:124
        today = 0x2350130
        local = 0x2350100
        span = 10791504
\#9  0x00000000004f8a20 in add_location_app (self=0x1dee1c0, app_id=0x232fef0 "org.gnome.Calendar", enabled=1, last_used=459618461810) at ../panels/privacy/cc-location-page.c:209
        data = 0xffffda80
        app_info = 0x2341c50
        t = 0x0
        row = 0x2348280
        w = 0x234fe00
        icon = 0x2345310
        last_used_str = 0x0
        desktop_id = 0x7fffcc034c30 "DL\310\375\a"
\#10 0x00000000004f8db4 in update_perm_store (self=0x1dee1c0, permissions=0x7fffcc04e2c0, permissions_data=0x7fffcc04ee80) at ../panels/privacy/cc-location-page.c:282
        enabled = 1
        last_used = 459618461810
        iter = {x = {140736616260288, 2, 0, 6386038, 140736616096608, 36922576, 16, 3579507750, 140737488345904, 140737350561909, 33733184, 36922576, 140737488345936, 140737350702366, 36922576, 3278251457363369984}}
        key = 0x232fef0 "org.gnome.Calendar"
        value = 0x7fffcc04e090
\#11 0x00000000004f8f4e in on_perm_store_lookup_done (source_object=0x1e24040, res=0x202ba40, user_data=0x1dee1c0) at ../panels/privacy/cc-location-page.c:324
        error = 0x0
        ret = 0x7fffcc04eef0
        permissions = 0x7fffcc04e2c0
        permissions_data = 0x7fffcc04ee80
\#12 0x00007ffff7e9082c in g_task_return_now () at /lib64/libgio-2.0.so.0
\#13 0x00007ffff7e944c3 in g_task_return () at /lib64/libgio-2.0.so.0
\#14 0x00007ffff7efe88b in reply_cb () at /lib64/libgio-2.0.so.0
\#15 0x00007ffff7e9082c in g_task_return_now () at /lib64/libgio-2.0.so.0
\#16 0x00007ffff7e944c3 in g_task_return () at /lib64/libgio-2.0.so.0

The timedate1_call will fail because network time synchronization is enabled:

GDBus.Error:org.freedesktop.timedate1.AutomaticTimeSyncEnabled: Automatic time synchronization is enabled

Let's not set_time when NTP is not available, neither set time by
accident at the widget construction stage. When widgets signals are connected
in the UI file their respective callback was getting called. By moving
the signal connection to callbacks to the widget's _init method we
avoid the unwanted callback call.

Fixes #2945

As the list of panels doesn't match the list of items in the model.

The System panel subpages used to be CcPanels. They still have
their own desktop file so that they can be findable in Search.

A future goal is to decouple our Search model from our panel list
model, so that we can better handle panel subpages and other more
grained search results.

Fixes #2930
Fixes #2974