Fix: make StaticDebugAndDisplay Send and Sync

[chris-ricketts]

Fixes #800

[apoelstra]

Nice. Yeah, I'm ok with this. In general I don't wanna throw every trait under the sun into this, but Send and Sync seem very reasonable, and if it makes the difference between anyhow compatibility and not we should do it.

Maaaybe I had some specific error types in mind that couldn't be Send/Sync, in which case I'll need to revisit this the next time I dust off my error improvement branch. But I don't think so.

[apoelstra]

ACK ea5b955; successfully ran local tests

[chris-ricketts]

Thanks for the quick review and merge @apoelstra!

Maaaybe I had some specific error types in mind that couldn't be Send/Sync, in which case I'll need to revisit this the next time I dust off my error improvement branch. But I don't think so.

On the topic of error improvement, I have a commit which attempts to refactor the descriptor::key::DescriptorKeyParseError by turning it into an enum as suggested in the FIXME comment:

rust-miniscript/src/descriptor/key.rs

Lines 327 to 330 in d0da327

	/// Descriptor Key parsing errors
	// FIXME: replace with error enums
	#[derive(Debug, PartialEq, Clone, Copy)]
	pub struct DescriptorKeyParseError(&'static str);

Would it be worth a PR?

My main motivation is to add support for Ypubs in descriptors and this was a prerequisite to do it right.

My plan is the follow the advice in rust-bitcoin/rust-bitcoin#2190 and change the version bytes before calling Xpub::decode in the parse_bip32_xpub function.

[apoelstra]

Would it be worth a PR?

This would be amazing. I've taken a few cracks at improving the global Error enum and never bothered touching DescriptorKeyParseError because it's self-contained and more of a chore than something that's blocking progress on the rest of the codebase.

My plan is the follow the advice in rust-bitcoin/rust-bitcoin#2190 and change the version bytes before calling Xpub::decode in the parse_bip32_xpub function.

Yeah, I still think that's the most reasonable way to approach this. (Given that I am still opposed to having any direct ypub/zpub support in this library. :))