Extend exclude config option

Hey! I'd like to re-request a feature previously requested in https://github.com/microsoft/pyright/issues/4461

Why? Pyright has an option to extend the config from another one. In our team, we have default linter configs that are shared across different repos via git submodule, because we need most of the settings everywhere. Then we extend those configs with additional settings that are repository-specific.

And here is the problem, since we need to exclude a specific directory, which is not covered by the general part of the config, we cannot exclude a path in addition to the base ones. The extend-exclude option would solve that issue, and that option is available in other linters configurations like Ruff or Black.

No files or tests are named in the issue. Start by tracing Pyright's configuration inheritance and existing exclude-option handling, then compare the requested behavior with issue #4461 and the referenced Ruff or Black options. Done means a repository-specific exclusion can be added while retaining exclusions from the extended configuration.

Written by the indexing model from the issue text.