Rustls 0.23

[stblr]

Since Rustls 0.23, the default cryptography provider was changed from aws-lc-rs to ring which could cause compatibility issues.

This PR also replaces rustls-native-certs with rustls-platform-verifier as recommended by Rustls devs.

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Because Cargo really wants to resolve all dependencies, even optional ones, to create the lock file, and because rustls-webpki 0.102 which is needed for all of this uses weak dependencies which are only available in Rust 1.60 in its Cargo.toml, I don't really see a way to update Rustls while keeping the Rust 1.48 MSRV.

[neonmoe]

That is pretty unfortunate. Maybe it's time to finally make a v3, since there could be dependents that are assuming all 2.x versions work with 1.48, as that's what's promised in the readme, and I wouldn't like to break their builds.

Another option would be to allow multiple versions of rustls, but I imagine that would require conditional compilation based on the version of rustls used, which I don't think can be done.

Open to any ideas. In any case, I'll try to come up with some solution that would allow keeping the msrv, because bumping the major version would be a pretty drastic change. So please hold, I'll come back to this in a while.

[neonmoe]

Sorry about the wait, I've decided on bumping the major version to 3.0. While doing the other changes, there was a minor conflict introduced, so I went ahead and merged this manually with the conflict fixed: b5571be. Thanks for the PR!