Optimize /datum/datacore/proc/manifest

[noelle-lavenza]

About the pull request

/datum/datacore/proc/manifest now uses an assoc lookup for valid job titles to make the looping step much faster.

Removes the sleep from manifest injection. It's entirely unnecessary, see here: tgstation/tgstation#20038

Explain why it's good for the game

No longer will there be an arbitrary 4 second pause before the manifest loads.

Testing Photographs and Procedure

Will take screenshots once I'm done PRing all the commits I've split out of #11826. I believe it was testmerged and no one reported issues with the manifest, though.

Screenshots & Videos

Put screenshots and videos here with an empty line between the screenshots and the <details> tags.

Changelog

🆑
code: removed an unnecessary pause before crew manifest generation
/:cl:

[fira]

I'm pretty sure last time i tried to shoot down a sleep involving datacore on roundstart, it resulted in a race condition. Job/Spawn code is an absolute mess and can't be relied upon.
I'd advocate for live testing this

[noelle-lavenza]

I'm pretty sure last time i tried to shoot down a sleep involving datacore on roundstart, it resulted in a race condition. Job/Spawn code is an absolute mess and can't be relied upon. I'd advocate for live testing this

theres a very real possibility that the whole thing needs a once-over, i think the biggest risk is that it works without the sleep on other codebases because they removed even more ones, or made something faster, or dont have as much pop, etc