refactors the asset subsystem to make it much more managed
adds support for 'deferred' assets for tgui, which will be later used
for things like tgui character setup and admin panels.
deferred means that it'll be 'sent in a timely manner after the ui
opens', as opposed to 'sent before the ui opens'
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Co-authored-by: silicons <no@you.cat>
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## About The Pull Request
Various asset systems I want in before more TGUI work. and also
byond-tracy support... and also light update debugging...
## Changelog
🆑
tweak: Chem Master UI has been reworked slightly.
