Disallowing a pull in PULL_PRESAVE does not stop the entity from being created.

Problem/Motivation

The PULL_PRESAVE description says: "Final chance for subscribers to prevent creation or alter a Drupal entity
during pull."
I have found this is not the case and that disallowing a pull does not stop the entity from being created.
It is clear why this happens from L585-595 of Drupal\salesforce_mapping\Entity\MappedObject.php

Steps to reproduce

• Trigger a pull on a new item.
• Interrupt the pull in the PULL_PRESAVE event using $event->disallowPull().
• The entity will be created even though the pull is disallowed.

Proposed resolution

I have made a patch that will check if the pull is disallowed, and if so it will not save the entity or the mapped_object.

Remaining tasks

Review and test