change uqint and vqint in atmos realm to new variables

[OB-IPSL]

We found out that the uqint and vqint variables in the atmos realm were pointing to CF variables that had no or limited physical meaning. In fact some CMIP6 groups already submitted a more meaningful vertical integral of the u * q and v * q that accounts for the air mass and did not follow the CF convention. We interacted with the CF folks so that two new variables have been created
integral_wrt_height_of_product_of_eastward_wind_and_mass_concentration_of_water_vapor_in_air and integral_wrt_height_of_product_of_northward_wind_and_mass_concentration_of_water_vapor_in_air

For CMIP7 it is recommended that uqint and vqint are scrapped and replaced by two new variables, eg uqmint and vqmint, that point to these new CF variables.

[martinjuckes]

See also #59