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 6ff90ff 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.

[therealprof]

Funny, on my MCUmeter (ARMv6-m) I'm actually seeing a slight pessimation in binary size:

-0.1%   6.2%   496B  embedded_graphics embedded_graphics::fonts::text::<impl embedded_graphics::drawable::Drawable<C> for &embedded_graphics::style::styled::Styled<embedded_graphics::fonts::text::Text,embed...
+0.1%   5.0%   400B  embedded_graphics embedded_graphics::fonts::text::<impl embedded_graphics::drawable::Drawable<C> for &embedded_graphics::style::styled::Styled<embedded_graphics::fonts::text::Text,embed...
+0.0%   3.7%   296B            ssd1306 ssd1306::properties::DisplayProperties<DI>::bounded_draw
-0.0%   2.6%   210B            ssd1306 ssd1306::properties::DisplayProperties<DI>::bounded_draw

but there's a new player on the field:

+0.0%   0.7%    52B          [Unknown] __aeabi_lmul

Anyway, looks nice on paper, is slight optimisation and offers ground for more optimisation so let's ship it.

[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!