Code suggestions group policy refactor

What does this MR do and why?

In Code suggestions API for SM users with SaaS red... (!122645 - closed) we decide to split the work:

• Part 1: Code suggestions group policy refactor (!123023 - merged)
• Part 2: Code suggestions API for SM users with SaaS red... (!123024 - merged)

In this MR I extracted the global policy change related to access_code_suggestion policy, and refactored specs related to this policy on code_suggestions API and old ai_assist API call.

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