Investigate wp-admin timeouts during publish and edit actions

[Clorith]

When using the backend to publish or edit a topic or reply, the publish/update process is agonizingly slow, and always ends in a 504 timeout error.

This also means that previewing isn't available, as the save needs to complete for a preview to load.

This would be great to track down and resolve, although the backend is rarely used, during releases processes it's convenient to be able to prepare the master list, with it's attached replies, ahead of time.

[dd32]

I haven't checked, but I'm almost certain this is one of the regular post-publish actions related to term counts - counting all the terms applied to all of the support forum threads/replies is not a fast task.

[Clorith]

Hmmm, then this may self-resolve if we address the topic tags situation in #5344

I'll try to get the finer details of that ticket down this weekend then, and finish the tag-conversion sheet to reduce the numbers, this seems very doable.

A discussion was had about it, just need to write down the details of that discussion in the ticket.

Will follow up on that ticket, and mark this one as maybelater for now, as it may not be needed, but don't want to lose track of it in case more investigative work is needed at that point.