Backports: Update 6.5.1

[cbravobernal]

What

Backports from 6.5.1.

• Enhancement - The Flexible Content “Expand All” and “Collapse All” button now appear correctly on mobile
• Enhancement - The Flexible Content delete layout button is now back in the main layout header, making it easier to delete layouts
• Enhancement - The JSON import tool now limits the selectable files to JSON files
• Fix - Disabled Flexible Content layouts are no longer counted towards min/max layout validation
• Fix - The top “Add Row” button for layouts is now disabled when layouts have reached the max layouts validation
• Fix - The per-layout “Add Row” and “Duplicate Layout” buttons are now disabled when layouts have reached the max layouts validation
• Fix - Disabling Flexible Content layouts no longer disables layouts in cloned Flexible Content fields using a different post ID on the same page
• Fix - Flexible Content “Add Layout” menu is no longer hidden by some field types
• Fix - Flexible Content layout names can now allow some safe HTML
• Fix - When creating a temporary post type during import, SCF now correctly sets the SCF post type, rather than defaulting to post