Adding edit AI Agent page

What does this MR do and why?

This MR continues the work in Ai Agents -- Experimental (&12330) to add the ability to edit properties of an Ai Agent. This edit screen loads the agent details from the GraphQL endpoint and persists updated data to the database.

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.

Screenshots or screen recordings

How to set up and validate locally

1. Ensure you have an EE license activated

2. Enable the feature flag

   Feature.enable(:agent_registry)

3. Load /-/ml/agents for any project (for example /flightjs/Flight/-/ml/agents) and click Create agent

4. Input an Agent Name and Prompt and click Create agent.

5. Load the edit screen at /-/ml/agents/ID/edit. Ensure the agent name and prompt you just created are shown in the input fields.

6. Make changes to the name and prompt and click Update agent.

7. Load the edit screen again at /-/ml/agents/ID/edit and ensure your changes are displayed.