python: render <svg> via _repr_html_

Work around a recent decision in Jupyter Lab and Notebook to render
<svg> is inline <img>, breaking tooltips or text selection.

(Rerendering all notebooks was painful.)

* NEWS: Mention the change.
* python/spot/__init__.py: Add a _repr_html_ method to all
classes that had a _repr_svg_.  It seems Jupyter will use
_repr_html_ by default.
* python/spot/jupyter.py: SVG replace the _repr_svg_ method
by a _repr_html.
* tests/python/_altscc.ipynb, tests/python/_autparserr.ipynb,
tests/python/_aux.ipynb, tests/python/_mealy.ipynb,
tests/python/_partitioned_relabel.ipynb,
tests/python/_product_susp.ipynb, tests/python/_product_weak.ipynb,
tests/python/_synthesis.ipynb, tests/python/aliases.ipynb,
tests/python/alternation.ipynb, tests/python/atva16-fig2a.ipynb,
tests/python/atva16-fig2b.ipynb, tests/python/automata-io.ipynb,
tests/python/automata.ipynb, tests/python/cav22-figs.ipynb,
tests/python/contains.ipynb, tests/python/decompose.ipynb,
tests/python/formulas.ipynb, tests/python/games.ipynb,
tests/python/gen.ipynb, tests/python/highlighting.ipynb,
tests/python/ltsmin-dve.ipynb, tests/python/ltsmin-pml.ipynb,
tests/python/parity.ipynb, tests/python/product.ipynb,
tests/python/randaut.ipynb, tests/python/satmin.ipynb,
tests/python/stutter-inv.ipynb, tests/python/synthesis.ipynb,
tests/python/testingaut.ipynb, tests/python/twagraph-internals.ipynb,
tests/python/word.ipynb, tests/python/zlktree.ipynb: Update all
notebooks.

NEWS

@@ -144,6 +144,17 @@ New in spot 2.11.6.dev  (not yet released)
   - Calling aut.get_hight_state(s) or get.highlight_edge(e) will
     return the highlight color of that state/edge or None.
 
+  - Recent version Jupyter Notebook and Jupyter Lab started to render
+    SVG elements using <img...> tag to make it easier to copy/paste
+    those image.  This breaks several usages, including the
+    possibility to have informative tooltips on states and edges (used
+    in Spot).  See the following issues for more details.
+      https://github.com/jupyter/notebook/issues/7114
+      https://github.com/jupyterlab/jupyterlab/issues/10464
+
+    This version of Spot now declares its svg outputs as HTML to
+    prevent Jypyter from wrapping them is images.
+
   Bugs fixed:
 
   - tgba_determinize()'s use_simulation option would cause it to