Update and/or add ESA CCI datasets required for CMUG OWP4.3

[morobking]

ESMValTool is planned to be used for CMUG OWP5.3 and 5.9 - as part of this CMUG OWP4.3 looks at updating or adding CCI datasets in ESMValTool

• Update Copernicus LAI to all timesteps every 10 days
• CCI Soil Moisture Gap-Filled product - base this on existing CCI SM cmoriser
• CCI Snow - Snow water equivalent
• CCI LST - combine 2 MW products to allow Growing Degree Days work form CMUG WP5.2
• Check CCI Above Ground Biomass is suitable for this work
• When available, implement CCI LAI Version 2 dataset

[morobking]

Branch created for CDS LAI cmoriser update to data V3: update_cds_lai_to_v3

[morobking]

Saving files causes issues - probably lazy data being realised.

[morobking]

Branch created for microwave CCI LST Cmorizing
https://github.com/ESMValGroup/ESMValTool/tree/cmorize_cci_mw_lst

[morobking]

Branch https://github.com/ESMValGroup/ESMValTool/tree/cmorize_cci_mw_lst now uses the ESACCI-LST.yml file to determine the platform/sensor separate to the file name.
Added ECT to give ascending and descending phase of orbit a different timestamp rather than using ts_day, ts_night as per pervious CMUG phases' work. ECT taken from https://space.oscar.wmo.int/satellites

Had to use iris.save not utils.save_variable because the filename given would not be unique, see esmvaltool/cmorizers/data/utilities.py (I have not modified this file)

This python file should work with the uncertainty variables defined in this currently open PR on ESMValCore ESMValGroup/ESMValCore#2458
Hence code to look at integer overflow issues with land cover type given in CCI LST is left here commented out ready to use in the future.

[morobking]

#4281 for the ESA CCI Soil Moisture GAPFILLED version being added to the existing COMBINED CMORiser.

[morobking]

Found some issues with the ERA5-Land reader for ESMValTool. Working on a fix so data with expver aux coordinate will load. Also found an issue around proleptic_gregorian vs standard calendar, this is simple to fix but need to ask is its actually a valid thing to do. Will open a separate ERA5-Land issue and start an ESMValCore branch for this.

[morobking]

Also need ERA5-Land and ERA5 data for this project. Some variables wont load with the existing ERA5. Starting a ESMValCore branch to fix this; coordinates appear to be the problem.