Add read_ep_address and make write_ep_address pub

[thalesfragoso]

This make it possible to re-use this to write other serial drivers, like an async one...

https://github.com/akiles/embassy/pull/75

[mvirkkunen]

Do you think it'd make sense to just go all the way and remove the read/write and such methods and just expose the entire endpoint objects via accessors or even pub fields? CdcAcmClass is meant to be used as a helper to implement other things anyways so hiding stuff probably isn't that important.

Also it'd be nice if global reformatting could be a separate commit so it's nicer to read 🙂 (I know the formatting is a mess right now, I can reformat it myself before next release)

[thalesfragoso]

Although I don't need to go all the way right now, I agree with you, it makes sense to even have them as pub, do you think this should be in this PR ?

Sorry for the formatting, it was automatic... I can remove it.

[ianrrees]

I like the idea of making the endpoints pub - ran in to the same issue in #21