feat(generative-ai): parse faker mappings from LLM CLOUDP-341206

[kpamaran]

Description

Update: This PR is being used as a loose reference to align on how to handle/unify the intermediary data structure(s) between the completion screen data, schema editor, faker script, and so on. Parts of it will be borrowed as needed

Adds a function that parses the LLM's structured output containing the fakerjs mappings that are turned into an executable factoryjs function.

The result of the Schema Editor component (tbd CLOUDP-333854) can be passed to parseFakerMappings, which may satisfy the type { fields: Array<FakerFieldMapping> } or be directly converted to it.

Current gap that can be addressed in another PR is that the probability field is not used.

Checklist

• New tests and/or benchmarks are included
• Documentation is changed or added
• If this change updates the UI, screenshots/videos are added and a design review is requested
• I have signed the MongoDB Contributor License Agreement (https://www.mongodb.com/legal/contributor-agreement)

Motivation and Context

• Bugfix
• New feature
• Dependency update
• Misc

Open Questions

Dependents

Types of changes

• Backport Needed
• Patch (non-breaking change which fixes an issue)
• Minor (non-breaking change which adds functionality)
• Major (fix or feature that would cause existing functionality to change)