Make autocomplete more performant
autocomplete_source.json is loaded for every single Issue and Merge Request. For this issue, it took more than a second to load and includes every single issue, user, and merge request in a given project. This can't be good for the site's speed, and is an extra (in this case) 175KB that shouldn't be loaded unless explicitly needed. For the gitlab-ce repository, it's more than 350KB! Unless I'm missing something that necessitates this, it should not be being served on every single page load.
Emoji are being served in the aforementioned autocomplete_source.json file as well as as an 813KB PNG sprite file. Which are we using, and why are we loading these twice?