chore: prepare v0.19.5 release

[vmx]

The plan would be to release a v0.19.5 version of the main multihash crate as it shouldn't really be a breaking change, it just changes internal implementations.

There is a large MSRV bump, but even Rust 1.81 is already over 1.5 years old. If someone really needs to support older versions, they can fix multihash to v0.19.4. If it turn out to be an issue for anyone, please open an issue.

@hanabi1224 As you can see my idea would be to release this as a patch release for multihash. Also patch releases for multihash-derive and multihash-derive-impl But release a minor for multihash-codetable, due to not implementing that custom Write for no-std. Does that sounds correct to you, or do you propose something else (you feedback would really be appreciated)?

[hanabi1224]

@vmx LGTM. Please note that I believe in theory, the change in multihash is breaking cid (only in no_std context). (cid requires the same Write trait from multihash. But we did patch release for no_std_io2 transition that I believe was breaking cid as well, and we could follow the same process with a fast follow-up cid release).

[vmx]

Very good points. Yes, let's do a cid patch release directly after and hope for then best :)

[vmx]

I've changed my mind and also did a patch release for multihash-codetable, so that just everything get upgraded automatically to the embedded no-std implementation instead of relying on no_std_io2 which can be seen as just a stop-gap.