mrc-4555: Add ability to save hintr output as duckdb database

[r-ash]

This PR will

• Add the ability to save hintr output as a duckdb database, based upon the file extension.

This will be used from hint to slice and read smaller portions of the data so we can deal better with large datasets (like for DRC)

[vimc-robot]

Thanks. Corresponding hintr PR at https://github.com/mrc-ide/hintr/pull/468