entity_operations_get_entity_operations_fieldset() now uses entity_operations_multiple_operation_form()

Entity Operations provides a helper function that builds a fieldset showing multiple operations for a given entity. The main use case for this is showing a set of operations in an entity render array for entity_view().

This fieldset was previously built as several forms, one for each operation. This has been changed to output a single form, using the existing form builder entity_operations_multiple_operation_form().