Leverage iOS 15 image decoding

[timonus]

iOS 15's new first party image decoding APIs appear to be faster and more memory efficient that the classic "draw image in context" method of image decoding. Would be nice to leverage this in TIP.

https://twitter.com/timonus/status/1450866353137618949

I plan to put up a PR for this at some point, haven't had time yet. I chatted with @NSProgrammer about this earlier today and he recommended opening a task tracking it!