Added Feature: CryptoProvider-independent code

[kraemv]

Hello everyone,
I want to extend rustls-compat to work with variable CryptoProviders.

The main changes are:

• Untied the CryptoProvider from the SSLCiphers, as the provider is not static. Now I use the rustls ciphersuite to get the protocol id of an SSLCipher, as rustls ciphersuites are static.
• Use the awl_lc_rs Ticketer explicitly, as this is not covered in the CryptoProvider API.

The main problem for switching the CryptoProvider in the old code was, that APIs outside the CryptoProvider API of rustls were used.

I am happy to discuss the changes!

[cpu]

Use the awl_lc_rs Ticketer explicitly, as this is not covered in the CryptoProvider API.

Some related discussions on this in rustls/rustls#1876

I wonder if given this crate's position in the ecosystem of rustls crates it might be better to avoid the crypto provider independence complexity until after the upstream rustls crate has finished more of the refactoring in-progress in that area. Especially if it could help avoid having aws-lc-rs dragged in just for the ticketer? 🤔

[kraemv]

I think covering the Ticketer with the CryptoProvider API would be helpful. As we can see from the discussion in rustls, there is a need for that, if we want to wrap the crypto in one provider.
Also, the API will change in future (CipherSuite fields...), so we can make the changes after rustls integrated the new API.
Still, I am wondering, if the ciphersuites must use the provider. If we only need the ID, that is already provided in rustls. I think the implementation of a variable provider in future will be easier, if we do not have the dependency between ciphersuite(information) and the provider.