Move duplicateTemplatePart action to the @wordpress/fields package

[gigitux]

What?

This PR migrates the duplicateTemplatePart action to the @wordpress/fields package. The primary issue with this action is its dependency on the CreateTemplatePartModalContents component, which resides in the @wordpress/editor package. Due to this, it can't be directly used within the @wordpress/fields package.

For the purpose of the @wordpress/fields package work, I have temporarily moved the component to this package. However, I'm not certain if this is the best long-term solution. Ideally, this component (and potentially others) should reside in a dedicated package, such as @wordpress/template, which would be more appropriate for components related to template and template-parts. A similar package for the patterns already exists: https://github.com/WordPress/gutenberg/blob/d6fcf4aea4aff17cf0910862bf10090e20ba2ab0/packages/patterns/src

Please review and provide feedback on whether this approach is suitable or if there are alternative recommendations for handling these dependencies. Thanks! 🙏 cc @youknowriad @oandregal

Testing Instructions

Ensure that Custom Dataviews is enabled.

1. Visit the Site Editor.
2. Visit the patterns view.
3. Click on header
4. Duplicate a header template part.
5. Ensure that the duplicated template part is created.

Testing Instructions for Keyboard

Screenshots or screencast

[gigitux]

This PR is ready to be reviewed! cc @oandregal @youknowriad @louwie17

[youknowriad]

Thanks LGTM

[gigitux]

Thanks LGTM

Thanks for your review! 🙇