Add sync methods to embassy-net

[chemicstry]

This adds sync alternatives to all embassy-net sockets in the try_xyz flavor. This allows using embassy-net in mixed sync/async environments.

[Dirbaio]

Looks good overall. 2 things:

• The naming for the "not ready yet" errors is a bit inconsistent. It's named Exhausted, BufferFull or WouldBlock depending on the place.
• Adding it to the error enums means the non-try methods can still potentially return them, users are forced to handle them uselessly.

Not sure what's the cleanest solution. One is to add enum TryError<T>{ WouldBlock, Other(T) }, and wrap the non-try errors with it everywhere. If you have other ideas i'm all ears.

[chemicstry]

The naming comes from smoltcp, I thought there is a reason for it, but maybe not. The only alternative I can think of is nb crate, but it seems that ecosystem is moving away from it? If not nb, I think your suggested TryError would be best. Let me know how to proceed.

[Dirbaio]

yes, let's avoid nb.

[chemicstry]

@Dirbaio this should be ready