Test launcher based on pytest

[svalat]

The problem

When running locally the full test suite (tests in /test of Idefix) we might want to avoid getting a long log with no summary of what passed and what failed.

What it does

In order a ease running the suite, I implemented a way to call the tests via the pytest library which is used to implement python unit tests. It offers by default :

• Summary logging (just SUCCESS if the test is valid)
• Filtering test to select what to run (eg. only MPI => -k mpi)
• Get a detailed output only for failed tests.
• Can get verbose mode (-v) if desired
• Get report in junit format which can be taken by github or we can generate an html page from it (via junit2html).

testme.json

I provided a way to describe the test running option combinations via a testme.json file which might be more readable
and less programmatic than the current testme.py.

Example:

{
     "variants": [
        {
            "dumpname": "dump.0001.dmp",
            "ini": ["idefix.ini","idefix-rkl.ini"],
            "noplot": true,
            "single": [false, true],
            "reconstruction": 2,
            "mpi": [false, true],
            "tolerance": 0
        }
    ]
}

This PR provides the testme.json equivalent to each testme.py in the test directory.

Documentation

I updated the documentation by adding a new dedicated page in doc/source/testing/testLauncher.rst

Missing

Make a default configuration for re-generate the reference results.

Legacy

I currently let untouched the current testme.py files to let the time to validate and complete the new process.

[glesur]

a few typos, but otherwise ok

[glesur]

Suggested change

	The class :doc:`idfxTest <idfxTest>` provides the basement to implement an *Idefix* integration test for validation.
	The class :doc:`idfxTest <idfxTest>` provides the toolbox to implement an *Idefix* integration test for validation.

[glesur]

Suggested change

	Before using :doc:`idfxTest <idfxTest>` you need to install some Python Depencencies (possibly in a ``virtual env``):
	Before using :doc:`idfxTest <idfxTest>` you need to install some Python depencencies (possibly in a ``virtual env``):

[glesur]

Suggested change

	When seeing an error, the output of the command will be printed at the end.
	When an error is detected, the output of the command will be printed at the end.

[glesur]

Suggested change

	The script is simply searching all the files names ``testme.json`` into the ``test`` directory.
	The script looks for all the files named ``testme.json`` in the ``test`` directory and all its sub-directories.

[glesur]

Suggested change

	This file describe the combination of parameters to use to produce the list of *Idefix* run to perform.
	This file describes the combination of parameters used to produce the list of *Idefix* runs to check.

[glesur]

Suggested change

	By default, the alphabetical order will be used.
	By default, the alphabetical order is used.