closes matplotlib#20001

Fixes matplotlib#20516

PGF's `random steps` decoration seems to be the most similar,
but does not exactly match the behaviour described in matplotlib's docs.
Therefore I repurposed the `randomness` argument as a seed to give
control on how the line looks afterwards.

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Switch documented deprecations in mathtext by `__getattr__` deprecations

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

…_output

API: rename draw_no_output to draw_without_rendering

Make warning for no-handles legend more explicit.

Remove unused HostAxes._get_legend_handles.

Redirect to new 3rd party packages page

legend_handler_map cleanups.

Clean up some Event class docs.

- parse() already normalizes prop=None to prop=FontProperties().
- We don't need to explicitly attach a canvas to a plain Figure() before
  calling savefig() anymore; FigureCanvasBase is always attached and
  handles the dispatching to the correct concrete canvas class.

According to the docs, this function was added in GTK 2.2, so probably
was only needed when we supported GTK2.

It also no longer exists in GTK4.

Since these examples don't need to support the very oldest GTK3, I took
the opportunity to rewrite them using the recommended Application-styled
model.

The `Gtk.Window.destroy` doesn't work, but `.close` correctly triggers
our cleanup.

ENH: Adding callbacks to Norms for update signals

BUG: Fix f_back is None handling

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

This hard codes the contents of the top bar which gets us out of the
trap that we want to have a different top-level structure to our complete
documentation than we want to have in the nav bar.

This makes them play much nicer with the navigation on the left side.