LFRic2UM pseudo-levels

### Are there any linked Issues or Pull Requests?

- ticket:916 (old trac ticket)
- #266 #434 #435

- is related to #445 and #467

### Brief description

Currently LFRic2UM cannot handle pseudo-levels at all. This ticket aims to add functionality for handling pseudo-levels at least by failing gracefully with a useful error message.

soil_levels in um2lfric is handled by having its own field kind w3_soil_field - see #435

land_tiles may be handled by the w3_field_2d field kind, but we're not sure.

snow_layers_and_tiles requires some restructuring after regridding, so that functionality will be added in its own ticket after this one - a placeholding log message will be added in this ticket

### Further details of the issue.

_No response_