ruff server does not load new configuration files when they are created

[snowsignal]

If you create a new pyproject.toml / ruff.toml configuration file in your workspace, we reload any existing configuration but do not 'register' the new configuration file.

This has been a known limitation of Index::reload_settings:

/// Reloads relevant existing settings files based on a changed settings file path.
/// This does not currently register new settings files.

[dhruvmanila]

I'm not sure whether this is actually a problem or not because it's suppose to be handled on the client side. The client will send us request on file events (create, change, delete). So, this should work.

[dhruvmanila]

As seen in the test plan of #12253, I'm creating a new pyproject.toml file in a nested folder and the diagnostics are being refreshed accordingly. At the end, I delete the file and it's refreshed as per the root pyproject.toml file.