Update toolchain and manifest to Rust 1.70.0

[mikedotexe]

I noticed this error when opening the repo:

So updated Cargo.toml and rust-toolchain in the project root from 1.69.0 » 1.70.0

This repo looks really amazing, btw, bravo!

[mooori]

Thank you for bringing this up! We have workarounds for building with 1.69 and use them in CI, but missed to highlight them to users.

We cannot yet bump the MSRV as some users of this crate still need to use Rust 1.69.0. To prevent issues like this, I’ve opened #131. After it lands, user with a toolchain >= 1.70.0 should not hit this issue anymore, as the override is removed from rust-toolchain (ref).

[mooori]

Closing as #131 has landed, which should resolve the issue for users with Rust >= 1.70. Users that need to use Rust < 1.70 can refer to #132.