add support for GFAS fire flux and proper management of grids, depending on which dataset is used (CEDS or CARBON_TRACKER)

mask ocean for CO2_land and land for CO2_ocean fluxes (need to check global conservation works as expected)

replacing toys models with a single general toy model

See merge request !2

toy model  supports YAML file input for ifs, nemo, and runoff via argument parsing, while also addressing the formatting issue in the YAML input file.

the toy model read the yamel file and works with  oasis - only tested for ifs, todo:  refactor, restructure in modules, logging and error handling

several changes for co2box model in tests/ : use global (not hemispheric) co2 box model and deactivate co2 emissions in IFS_mock.py ; updates to convert-ece4pyreader-grids.sh

several changes for co2box model in sources/data-coupler/ : various bugfixes and more logging ; rename oasisIn to oasisOut ; allow option to accumulate and add fields (e.g. emissions) or only read field for first timestep (e.g. initial co2) ; add constants and named scale factors (e.g. co2_ppm_to_mass) ; use global (not hemispheric) co2 box model

basic refactoring with new OasisOutVar (handling update and send internally) and renaming DataCouplerVar class to FileInputVar