preserve $node->original for hook_node_postsave for 8.x-1.2

The same issue was also reported on previous versions of D7 (7.x-1.0-beta2)

By taking reference pf that issue created patch for current version.
It worked for me.

Update patch

The last patch did not apply due to incorrect directory references, so i made an updated one. Also updated some styleguide issues as phpstan was complaining.