ruff

57be814a - ruff_db: add method to create sub-diagnostics from old secondary messages

ruff_db: add method to create sub-diagnostics from old secondary messages This is temporary to scaffold the refactor. The main idea is that we want to take the `InferContext` API, *as it is*, and migrate that to the new diagnostic data model *internally*. Then we can rip out the old stuff and iterate on the API.