CMIP7: Region should be linked to grid and grid_label

[mo-jareddrayton]

Currently set manually in the demonstrator mip_convert.cfg.

CDDS/demonstrator/mip_convert.cfg

Lines 37 to 38 in 574dd77

	# region should be linked to grid and grid_label
	region = glb

This should probably be set during the configure step.

Also it should be noted that the cmip7_grid.py is just a duplication of those in `cmip6``

CDDS/cdds/cdds/common/plugins/cmip7/cmip7_grid.py

Lines 38 to 46 in 574dd77

	NATIVE = 'native', 'gn', False
	NATIVE_ZONAL = 'native-zonal', 'gnz', False
	REGRIDDED = 'regridded', 'gr', False
	GLOBAL_MEAN = 'global-mean', 'gm', False
	UGRID = 'ugrid', 'gn', True
	VGRID = 'vgrid', 'gn', True
	UVGRID = 'uvgrid', 'gn', True
	UVGRID_ZONAL = 'uvgrid-zonal', 'gnz', True
	SITES = 'sites', 'gn', False

CMIP7 regions - https://github.com/WCRP-CMIP/CMIP7-CVs/blob/main/cmor/cmip7_region.json