Use iterators in interface send methods

[jamwaffles]

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PR description

Switches some for loops for iterators to speed up sends (and hopefully reduce code size) by eliding bounds checks.

[jamwaffles]

I just added some optimisations in 6ff90ff2abcb172db11e0d4540f8c2fcf70a4349 which should make set_pixel calls a lot faster. Unsure how to bench, but for one thing the change from an if/else to bit manip ops to set the pixel value in a byte should be much faster now. The generated assembly says so.

[jamwaffles]

Yeah, slightly bigger but maybe faster so worth it in the end? I dunno tbh, it's all tradeoffs lol. Thanks for the review!