FieldWebform DataProducer fails to return webforms due to incorrect access checking

Improvements:

Change from 'view' to 'submission_create' operation in filterAccessible() to properly handle webform-specific access logic. This aligns with how the webform module handles access checking in preRenderWebformElement and ensures webforms are accessible through GraphQL when they should be available for submission.

Fixes webform entity reference fields not returning webforms due to incorrect access operation.

Closes #3532755