Moved the legal warning into a slot

What does this MR do and why?

Moved the legal warning in the AiGenieChat component into a slot. This is to have flexibility for different groups to treat it as a possible entry for legal information specific to those groups. At the moment we have two legal notifications:

"Responses generated by AI"	The information not allowing copy/pasting code into GitLab codebase (default)

In the course of the unification of the AiGenieChat component, we should allow different groups to supply legal information relevant to their group.

⚠ this change makes even the second type of the legal warning sticky

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the following feature flags:
   • explain_code_snippet
   • explain_code_chat ⚠ this is the flag that works separately from all others and only controls the chat
   • openai_experimentation
   • ai_experimentation_api
2. Add an OpenAI API key by following the steps in !116364 (merged)
3. Simulate the GDK to simulate SaaS and ensure the group you want to test has an Ultimate license
4. Enable Experimental features and Third-party AI services
   1. Go to the group with the Ultimate license
   2. Group Settings > General -> Permissions and group features
   3. Enable Experiment features
   4. Enable Third-party AI services
   5. Save settings
5. Open a file containing Source Code (Note, this file should not be from the GitLab codebase).
   • sample_file.js
6. Highlight some of the Source Code.
7. Click on the (?) button in the gutter to the left of the source code.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #410114