Remove std

[Christiaan676]

Changes to:

• Switch to core::error::Error
• Remove std feature
• Fixed two Clippy warnings

As requested in #74

Changes do bump the MSRV to 1.81 as core::error was stabilized in this release.

[newpavlov]

The MSRV bump is a viral change which will affect almost all our crates. Are we sure that we want such drastic bump? After all, it's the latest stable released only several days ago.

Personally, I am on the fence. It's certainly nice to be able to remove the std feature from many crates and it may allow us to use some recently stabilized features, but the MSRV bump is a significant price to pay for that which is likely to affect a lot of our users.

[newpavlov]

I think it's better to use just 1.81 here.

[Christiaan676]

Unfortunately the documentation on rust-version only mentions that two or three components is allowed. Not if they are handled differently.

Can you explain why the two components version is better? (if needed I can create a MR to change it)

[newpavlov]

It's the same logic as with skipping zero minor/patch versions in dependencies (e.g. we use zeroize = "1.8", not zeroize = "1.8.0"). The notations mean the same thing, but 1.81 is shorter and easier to read. I think it can be updated in a pre-release PR.

[tarcieri]

@newpavlov I think we should generally get this change into the next set of crates, even if it's an aggressive MSRV bump. If people don't want the bump, they can stick with the last stable series of releases.

I am down to hold off on releasing crates until such a time as this seems less drastic than it is today. Generally the ecosystem seems to have converged on stable - 3 as a satisfactory release window for people who aren't sticking with the antiquated "whatever Debian stable is" window (IIRC Rust 1.63, but speaking as a Debian stable user that's far too old to be useful for me and I install via rustup).

That would put the release timeframe around December 2024.

[tarcieri]

Here's a PR to fix the version: #87