Add new class with stage check for AI features

What does this MR do and why?

Describe in detail what your merge request does and why.

Screenshots or screen recordings

Currently, checks for namespace_settings.experimental_features_enabled and namespace_settings.third_party_ai_features_enabled were scattered all over codebase.

This class allows for easy check and single source of truth for checking on which stage feature is. Also: with this new class moving feature from experimental to beta would be extremely easy.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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