test: add usage of jsonschema to validate the testme.json file and get more understandable errors.

[svalat]

This PR adds format validation for the testme.json files about the test suite to get more understandable errors in case of invalid format, wrong values....

It is based on jsonschema a standard way to validate JSON / YAML files : https://json-schema.org/.

Example of error : invalid value

--------------- testme.json format error ---------------
Invalid format for : /home/........./idefix/test/MHD/AmbipolarCshock3D/testme.json
'no' is not of type 'boolean'

Failed validating 'type' in schema['properties']['default']['properties']['single']:
    {'type': 'boolean'}

On instance['default']['single']:
    'no'
--------------------------------------------------------

Example of error : wrong property name

--------------- testme.json format error ---------------
Invalid format for : /home/................/idefix/test/MHD/AmbipolarCshock3D/testme.json
Additional properties are not allowed ('tlrance' was unexpected)

Failed validating 'additionalProperties' in schema['properties']['default']:
    {'type': 'object',
     'additionalProperties': False,
     'properties': {'ini': {'type': 'string'},
                    'definitionFile': {'type': 'string'},
                    'dumpname': {'type': 'string'},
                    'tolerance': {'type': 'number'},
                    'nonRegressionTest': {'type': 'boolean'},
                    'standardTest': {'type': 'boolean'},
                    'noplot': {'type': 'boolean'},
                    'reconstruction': {'type': 'integer'},
                    'dec': {'type': 'array', 'items': {'type': 'number'}},
                    'single': {'type': 'boolean'},
                    'vectPot': {'type': 'boolean'},
                    'mpi': {'type': 'boolean'},
                    'restart': {'type': 'boolean'},
                    'callPyFunctionBefore': {'type': 'string'},
                    'callPyFunctionAfter': {'type': 'string'},
                    'check_file_produced': {'type': 'array',
                                            'items': {'type': 'string'}},
                    'restart_no_overwrite': {'type': 'array',
                                             'items': {'type': 'string'}}}}

On instance['default']:
    {'dumpname': 'dump.0001.dmp',
     'noplot': True,
     'single': False,
     'reconstruction': 2,
     'tlrance': 3e-14}
--------------------------------------------------------

[glesur]

Would it be possible to validate the json file as a pre-commit action? at the moment, no externally-triggered action can launch _validateNaming, while I believe this could be useful on a systematic basis.

[svalat]

Done.
There is now two checks in the pre-commit :

1. Validation via the jsonschema
2. Call ./test.py --validate-testme-json which also pass by _validateNaming.

Note: it is triggered only when there are changes in testme.json files.

Note: there is also a change in test.py implementation to make it faster (in precommit call as for execution).