Add raw random noise example

[jamwaffles]

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

• Check that you've added documentation to any new methods
• Rebase from master if you're not already up to date
• Add or modify an example if there are changes to the public API
• Add a CHANGELOG.md entry in the Unreleased section under the appropriate heading (Added, Fixed, Changed, etc)
• Run rustfmt on the project with cargo fmt --all - CI will not pass without this step
• Check that your branch is up to date with master and that CI is passing once the PR is opened

PR description

This is the result of an email discussion with @nebelgrau77 who is asking for assistance sending raw bytes to the display, without using GraphicsMode, etc. The example emulates an old TV with a white noise effect using random crap from the rand crate in no-std mode.

[jamwaffles]

@therealprof This raises the question of moving some common stuff in the crate like initialisation routines into a trait so that all modes (including RawMode can use them). Let's leave that for another PR, but it's food for thought.

[therealprof]

@jamwaffles Yes, I'm very up for that. Also we might want to reconsider the use of traits and maybe move to a simple enum instead for better code optimisation.

[therealprof]

It would be great if we could slowly move to edition 2018 code. 😅

I also don't quite see the point of using semihosting in examples like this which only adds another stumbling block without any benefits.

[jamwaffles]

Yeah I want to upgrade all the examples in one big PR. Those imports are bugging me.

I also don't quite see the point of using semihosting in examples like this

What would be a better panic_* to use in your opinion?

[therealprof]

panic_halt or panic_abort.

[therealprof]

Other than those nits which we can also address separately, this looks good to me.

[therealprof]

Hm, I thought you re-enabled the regular merge feature? I can only squash and merge.

[jamwaffles]

Hm, I thought you re-enabled the regular merge feature? I can only squash and merge.

Hasn't that always been the case? At any rate, that's what I'd prefer to do anyway.

[therealprof]

Hasn't that always been the case? At any rate, that's what I'd prefer to do anyway.

Rewriting the commits and autosquashing it means you're causing problems for people with work-in-progress stuff. I was hoping that the setting I recently recommended would only prevent merges of PRs with merges in them which is the bad stuff, but it seems it disables all merge commits.