Increase MSRV for all crates

[thejpster]

Our MSRV is variously 1.61, 1.71 or 1.81 depending on which crate you look at, all of which are pretty old. This blocks us from adopting newer language features, like #531.

Let's move to 1.85 across the board, with Edition 2024. No-one should be using a compiler older than that.

For reference, Ferrocene 26.02 is based on Rust 1.92, and Ferrocene 25.11 is based on Rust 1.90.

We should:

• Update all the crates in this repo to edition 2024
• Update the package.rust-version attribute to 1.85
• Remove the deprecated package.authors attribute
• Update all the READMEs to note that the MSRV is recorded in the Cargo.toml file
• Add an entry to all the CHANGELOG.md files to note the MSRV change (in an Unreleased section, which will get moved to the appropriate section when the release is made)

[wt]

I would like to be assigned this one please.

Do we have consensus on the 1.85 MSRV?

[wt]

I think there are reasons that we may want to separate the edition 2024 move into a separate issue. Would that be okay?

[wt]

Also, need to update the tests to always test the cortex-m-types.