Matthew Pickering authored Dec 26, 2022 and Marge Bot committed Jan 24, 2023

Currently the driver diagnostics don't give any indication about which unit they correspond to.

For example `-Wmissing-home-modules` can fire multiple times for each different home unit and gives no indication about which unit it's actually reporting about.

Perhaps a longer term fix is to generalise the providence information away from a SrcSpan so that these kind of whole project errors can be reported with an accurate provenance. For now we can just include the `UnitId` in the error message.

Fixes #22678