Vicinity CLI using option to prevent addition of cell method

[bayliffe]

Test of vicinity CLI applied using option to exclude the addition of an area cell method.
Data is a simple copy of the existing kgo_10000.nc file without the cell_method present.

probability_of_number_of_lightning_flashes_per_unit_area_in_vicinity_above_threshold / (1) (realization: 4; projection_y_coordinate: 100; projection_x_coordinate: 100)
    Dimension coordinates:
        realization                                                                                    x                           -                             -
        projection_y_coordinate                                                                        -                           x                             -
        projection_x_coordinate                                                                        -                           -                             x
    Scalar coordinates:
        forecast_period                                                                    7200 seconds, bound=(3600, 7200) seconds
        forecast_reference_time                                                            2022-06-28 00:00:00
        number_of_lightning_flashes_per_unit_area                                          0.0 m-2
        radius_of_vicinity                                                                 10000.0 m
        time                                                                               2022-06-28 02:00:00, bound=(2022-06-28 01:00:00, 2022-06-28 02:00:00)
    Attributes:
        Conventions                                                                        'CF-1.7'
        institution                                                                        'Met Office'
        mosg__model_configuration                                                          'gl_ens'
        source                                                                             'Met Office Unified Model'
        title                                                                              'MOGREPS-G Forecast on UK 2 km Standard Grid'

[cpelley]

perhaps change to targeting your new 1.17.x branch??
(then merge 1.17.x into master after this is merged perhaps)

[gavinevans]

For clarity, with this improver PR targeting master directly: metoppv/improver#2296, both this PR (targeting master) and #122 are required.

[gavinevans]

Thanks @bayliffe 👍

[MoseleyS]

This PR needs the changes from #122 adding in as well so that the tests associated with metoppv/improver#2296 can all pass.