Collect feedback on natural language querying feature

What does this MR do and why?

Adds a feedback mechanism for the natural language querying feature within the product analytics visualization designer.

The new feedback form is shown after generating a query. After submitting feedback, a confirmation message is shown. Generating a new query resets the feedback form.

A promptId (UUID generated for each prompt submission) is sent with each feedback to (eventually) allow relating the feedback with the specific prompt.

Feedback is sent as InternalEvents, with the following values:

• user_feedback_gitlab_duo_query_in_visualization_designer_helpful
• user_feedback_gitlab_duo_query_in_visualization_designer_unhelpful
• user_feedback_gitlab_duo_query_in_visualization_designer_wrong

Additionally the following metrics have been created:

• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_helpful_weekly
• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_helpful_monthly
• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_unhelpful_weekly
• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_unhelpful_monthly
• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_wrong_weekly
• counts.count_total_user_feedback_gitlab_duo_query_in_visualization_designer_wrong_monthly

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

Before	After
	(after generating query)
	(acknowledgement tooltip)
	(after submitting feedback)
	(form reset after generating a new query)
	(form wrapping at smaller viewports)
	(wrapping at smaller viewports once submitted)

How to set up and validate locally

Apply setup steps for backend MR which introduced the AI feature:

• Enable AI features locally: https://docs.gitlab.com/ee/development/ai_features/#test-ai-features-locally
• Make sure you've enabled Vertex access and configured it with your GDK. This action does not use Anthropic's API, only Vertex.
• Enable the :generate_cube_query flag locally. NEW

Then:

1. Follow these instructions to setup Product Analytics in GDK.
2. Onboard Product Analytics by setting up the feature at Project > Analytics > Analytics dashboards.
3. Visit the visualization designer at Project > Analytics > Analytics dashboards > Visualization designer.
4. Enter prompts in the UI, and verify the new feedback form.

Related to #442058 (closed)