Simplify downloading osm buildings data for specific region

[davide-f]

Describe the feature you'd like to see

Downloading buildings for large countries is likely prohibitive.
An interesting approach by bobby here: https://github.com/PyPSA/pypsa-eur/pull/1079/files#diff-7b12ab7b9a03eb826142c26bb9d80c8c32bf66e30eb0996b0b482946a6ad38f4
allows to download osm data using various filtering options that are performed on the server rather than the local computer.
This can allow to retrieve the data only for the specific region of interest rather than the entire country.
This technique can be explored to reduce the requirements for distribution