Refactor tag scripts to fix multiple issues:
* Errors during tag scripting didn't show the actual error message, just
a generic "There was an error updating post #NNN" message.
* The quick edit form didn't show any error messages at all on failure.
* Thumbnails didn't have all their data attributes properly updated
after the post was updated.
This changes it so that thumbnails have their html fully replaced after
updating. This has the side effect of removing event handlers bound
directly to the thumbnail. A `danbooru:post-preview-updated` event is
fired in case userscripts need to detect when thumbnails are updated.
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