Add export/import functionality for forms (transferability) #1425

Nextcloud (please complete the following information):

• Nextcloud-Version: 25.0.2
• Forms-Version: 3.0.1

Is your feature request related to a problem? Please describe.
I cannot transfer a form from one Nextcloud instance to another.

Describe the solution you'd like
I would like to be able to export a form (or all forms or selected forms) to an editable file, e. g., XML or JSON, and then import the form(s) via that file into another or even the same Nextcloud instance.

Describe alternatives you've considered
None

Additional context
None