In preparation for adding new rate limits for unauthenticated API
requests, we add `_web_` to the attributes for the current general
unauthenticated rate limits in the application settings API:

- `throttle_unauthenticated(_web)_enabled`
- `throttle_unauthenticated(_web)_period_in_seconds`
- `throttle_unauthenticated(_web)_requests_per_period`

The API is changed to accept and return both the old and new names.

We'll rename the actual DB columns in a future issue, see
https://gitlab.com/gitlab-org/gitlab/-/issues/340031 for details.

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/335300
Changelog: changed