"Save and edit layout" button added to any entity forms (except "delete" form)

Problem/Motivation

#3246699: Add "Save and Edit Layout" button to entity edit pages introduced the Save and edit layout button on create and edit entity forms. Unfortunately the if-condition that checks for an instance of ContentEntityFormInterface results in the button being added to any entity form implementing that interface (except the delete form of course)

Steps to reproduce

• Install layout_builder_save_and_edit module
• Build a custom entity form class that implements ContentEntityFormInterface or extends ContentEntityForm class for an entity type/bundle that has layout builder with overrides enabled
• Create a route that displays that form -> see the Save and edit layout button being added

Proposed resolution

• Ensure that the Save and edit layout button is only added entity forms for relevant operations (e.g. see access_unpublished module code for a similar solution at https://git.drupalcode.org/project/access_unpublished/-/blob/8.x-1.x/src...

Remaining tasks

• Create a patch/MR that fixes this issue

User interface changes

• Save and edit layout button will only be added to relevant forms anymore

API changes

n/a

Data model changes

n/a