Add unit primitive and permission checks for summarize review feature

What does this MR do and why?

• This MR adds self-managed support and access control (unit primitive) for Code Review Summary feature.
• This guide was followed for making the required changes.

Verifications:

• Unit primitive for the summarize_review feature already exists in the gitlab-cloud-connector repo: summarize_review.yml ✅
• There is already an entry for summarize_review in access_data.yml ✅
• summarize_review is added as one of the unit primitives for anthropic_proxy in access_data.yml ✅
• There is no need to add unit tests for access data spec because of the refactor done in this MR: !169133 (merged) ✅

Follow-up MR goals:

• Update summarize_review in AI Catalogue:

summarize_review: {
  ...
  self_managed: true,
  ...
}

• Update necessary docs

How to set up and validate locally

Prerequisites

• Make sure you've setup local AI features by following this guide

Steps

• Run GDK with AI features locally
• Create (or open an existing) MR
• Start a review and add bunch of comments
• During finalize code review step, ensure that Add Summary button is accessible and working as expected

Screenshot

• Make sure the summarize code review feature is still working as expected

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #495657 (closed)