Issue #3609102 by bstallings: Fix deprecated drupal_set_message() calls

Ben Stallingsrequested to merge
issue/entity-3609102:3609102-function-drupalsetmessage-not into 8.x-1.x

Replace drupal_set_message() with MessengerInterface::addMessage()/addError() in RevisionableContentEntityForm::save().

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com

Closes #3609102

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