refactor(editor): Migrate workflows store to setup function with composition API (no-changelog)

[alexgrozav]

Summary

In order to have better type safety and better caching, we're rewriting the workflows store to use composition api.

Related tickets and issues

https://linear.app/n8n/issue/N8N-7380/migrate-workflows-store-to-composition-api

Review / Merge checklist

• [x] PR title and summary are descriptive. Remember, the title automatically goes into the changelog. Use (no-changelog) otherwise. (conventions)
• [x] Docs updated or follow-up ticket created.
• [x] Tests included.

  A bug is not considered fixed, unless a test is added to prevent it from happening again. A feature is not complete without tests.