Bug fix: correct sign of variation of Rossby number and radius. We
have to be consistent with the computation of `delta_ro_mean` and
`delta_r_mean`. `delta_ro_mean` and `delta_r_mean` were computed by
subtracting origin from tail.

It does not make sense here to assume an ellipsoid: the computation of
the distance with $\cos \phi \delta \lambda$ and $\delta \phi$ is a
rougher approximation than treating the Earth as a sphere.

We avoid multiple conversions to rad of the same value, in the loop on
edges, since a segment can be head or tail of several edges.

Move functions `node_to_date_eddy` and `date_eddy_to_node` from script
`report_graph.py` to script `util_eddies.py`. `util_eddies.py`
contains more basic functions, it only imports
shapefile. `report_graph.py` imports networkx. It was not convenient
nor meaningful to require networkx for scripts that use
`node_to_date_eddy` or `date_eddy_to_node`.

Useless: there is a symlink to `util_eddies.py` in directory Overlap
since commit 56ca8ea3.

Read orientation from `expanded_traj.json`.

Installation has been tested with CMake `3.27`. Adding the maximum
version rids us of a warning message concerning policy CMP0144.

This seems to be a little faster, even if we do not use out-degree for
all the nodes. For `Global_1993_2023/Graph_anti`, this commit reduces the time
to define `traj_prop` from 23 s to 20 s.

We know that we are going to need in-degree for every node of the
graph. For `Global_1993_2023/Graph_anti`, this commit reduces the time
to define `traj_prop` from 31 s to 25 s.

This looked good but was much longer. For example, for
`Global_1993_2023/Graph_anti`, this commit reduces elapsed time
approximately from 24 mn to 2 mn.

This makes quite a difference in file size for a large domain. For
example, the size of `Global_1993_2023/Graph_anti/expanded_traj.json`
is reduced from 0.6 to 0.3 GiB. We do not need pretty display for
these files.

This is convenient for scripts `plot_traj.py`, `filter_traj.py` and
for hacking with function `get_duration` of `plot_traj.py`.

As an exception to our general philosophy, we prefer here to use as
input the results from previous tests in the current series of tests
because these are performance tests that we want to try with different
sizes of edgelist. We do not want to run the tests three times to have
the performance for a new size of edgelist.

So we can better distinguish initial position from small islands on
the map.

Move functions `plot_distr_funct`, `fig_hist` and `fig_distr_funct` to
module `jumble_matplotlib`, out of this repository, because they are
of more general interest.

This is case 2 correction in the Matlab program of Rémi Laxenaire.

The test is useless in this version since we know `traj_prop[n] == -
1` at the beginning of the iteration, but we are preparing to process
phantom patterns.

Preparing to process phantom patterns.