Add best practice step for Field Agent

Problem/Motivation

Currently the field agent is:
Figuring out what fields you want to create/edit or if you have questions. It can give slight suggestions during this initial query, but just in terms of what field to choose when the user prompt is disambiguous.

Then for each field if wants to create or edit:
Figuring out for each field a storage settings (only create).
Figuring out field config, form config and display config.

Since the input context size of the initial query will not handle the context size of best practice we should add a step between these two parts where we can inject a best practice prompt for a field if it exists where it can suggest best practices and that you have to confirm that you don't want to follow them or pass it through for creationg/editing.

With memory settings any seasoned Drupal developer, can add overrides when they know that they want to go against suggested best practices, see https://www.drupal.org/project/ai_agents/issues/3487427 ✨ Memory settings Active , to make sure that this does not get annoying.

Proposed resolution

Add an optional possible best practice prompt per field type, that can give feedback and suggestions based on the user prompt.

Remaining tasks

User interface changes

API changes

Data model changes