Apply search rate limits to search scope

What does this MR do and why?

The changes in this MR are behind the feature flag search_rate_limited_scopes

Because every search in the UI typically runs concurrent searches with different scopes to get counts, we apply rate limits on the search scope if it is present.

If an abusive search is detected, we have stricter limits and ignore the search scope.

👉 The thought behind this MR is once we have limits per scope, we then have the option to restrict the limits to a less generous number.

The default limit for authenticated requests is 300 searches / minute.

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