Upgrade bitcoin to v0.31

[tcharding]

Upgrade dependencies to use the latest rust-bitcoin v0.31.

While we are at it, bump the crate version ready for release.

(Includes pinning dependencies for MSRV build in CI.)

[tcharding]

Excuse the noise, this is another go at #78 because I saw #76.

This is #60 with pinning in CI. I previously handed off to @getong because he did #74 but that seems to be stalling. Lets see if I can get this past CI.

I copied the pinning done by @notmandatory's PR and tweaked it a bit after upgrading the electrsd dependency.

[tcharding]

I left, zstd and zstd-sys in there, likely unnecessary but the additional explicitness doesn't hurt. Will remove if anyone really wants it gone.

[tcharding]

Thanks for the review @tnull!

[notmandatory]

I've merged #76 so this should be rebased on master so we just see e41b360876fa4f6dcc6bcffe5cf1d5ba716e942f.

[tcharding]

Done, thanks.

[coveralls]

Pull Request Test Coverage Report for Build 7896060347

Details

• -3 of 3 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 78.934%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/api.rs	0	3	0.0%
<!--	Total:	0	3	0.0%	-->

Totals
Change from base Build 7822386543:	0.0%
Covered Lines:	918
Relevant Lines:	1163

---

💛 - Coveralls

[notmandatory]

Overall looks good to me, just need to resolve above comments about zstd.

@tnull is it OK with you to merge this one before #75? This one is a smaller change so should be easier to rebase on top of.

[tnull]

Overall looks good to me, just need to resolve above comments about zstd.

@tnull is it OK with you to merge this one before #75? This one is a smaller change so should be easier to rebase on top of.

Sure, happy to rebase once this landed!

[tcharding]

You guys were right about the pins, thanks for pushing me.