Allow table names to be completed with leading schema names

[rolandwalker]

Description

Allow table names to be completed with a leading schema name as in

schema.table

Note however that the table names can only be successfully completed if they are in the currently-selected schema. Completing table names in another schema is still a todo.

This is a one-line fix that appears to be due to a confusion between the strings "database" and "schema" in the completion code.

Strictly speaking this fixes #1142, but not #109.

Checklist

• I've added this contribution to the changelog.md.
• I've added my name to the AUTHORS file (or it's already there).
• I ran uv run ruff check && uv run ruff format && uv run mypy --install-types . to lint and format the code.

[scottnemes]

Side effect of this appears to be that it now suggests databases along with tables, which isn't super useful since you can't currently get suggestions for tables in other databases as you mentioned. Also imagine we'd want tables to be listed first anyway, as I think you are more likely to want a table vs another database:

So might be worth putting this off until after completions are available for other schemas, otherwise I think it makes it less user friendly at first glance anyway.