Fix terminal mode

[bugadani]

Hi! Thank you for helping out with SSD1306 development! Please:

• [x] Check that you've added documentation to any new methods
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• [x] Add or modify an example if there are changes to the public API
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PR description

~I had a go with #85 and failed miserably. But while doing so, I discovered the driver crashes with 90° rotation. This PR fixes that crash, but does nothing to fix the rotation issue.~

The issue is, properties.get_dimension flips width and height but set_draw_area expects them in the original order. I think for clearing it doesn't matter which direction we go, so I'm using the original physical size instead.

This is a performance hit, because every cursor move sends several display commands, but all the rotation values are rendered correctly.

[jamwaffles]

This fixes the clear issue, but the terminal_i2c demo crashes if I add .with_rotation(DisplayRotation::Rotate90) or .with_rotation(DisplayRotation::Rotate270) to it with this odd result:

I haven't had time to investigate but it would be great to fix this new crash in this PR as well, even if the characters remain garbled.

[bugadani]

Thanks I forgot to fill my screen to see if there's anything more fishy. Current code writes in the correct direction but newline handling is still incorrect and characters are rotated.

[bugadani]

I've fixed the whole thing instead. Code quality could use some love, but hey, priorities :)

Closes #85

[therealprof]

@therealprof you were the original author of TerminalMode so I'll let you approve and merge this PR if you're happy with it.

I was afraid you would say that. 😅

[bugadani]

reset_pos still needs to be checked, and the docs updated, so take your time :)

[bugadani]

Once CI is happy, this is ready for review

[jamwaffles]

Awesome. I'll do a release later this evening. Thanks for your patience all!