pft dimension to vegtype

The CMIP7 data requests includes land variables with the dimension vegtype. vegtype does not exactly match the fates pft-classes, but there is a nice mapping of 1 or more pft to each vegtype. We can solve this with adding a hook in the yaml-creation for variables that include this dimension that maps pft to vegtype as we do with sumoverpfts, and then we would simply need to implement this function to map and reorder the dimensions correctly.

"In CMIP7, the vegtype coordinate, instead, requests values for seven specific vegetation categories (namely broadleaf_deciduous_trees, broadleaf_evergreen_trees, needleleaf_deciduous_trees, needleleaf_evergreen_tree, natural_grasses, crops, and shrubs) to enhance the comparability among models and processes understanding (e.g. Li et al., 2024b)."

[CMIP7 land data request](https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3207/egusphere-2025-3207.pdf)

Start by locating the YAML-creation hook for variables containing the vegtype dimension and the existing sumoverpfts handling. Review how FATES PFT classes are represented, then determine the mapping to the seven CMIP7 vegetation categories and verify that dimensions are mapped and reordered correctly.

Written by the indexing model from the issue text.