Update crypto deps and add a new Cipher associated type

[Nashtare]

Description

This PR generalizes the use of AES to any AEAD, to be used during share encryption, and updates the mode used in testing to be AES-GCM.

Additions and Changes

The outstanding changes are:

• a new associated type to CipherSuite, namely Cipher, to be used during Dkg / Resharing to encrypt/decrypt secret shares. It must implement the Aead (for (de/en)crypting) and KeyInit (for Key initialization from the output of the HKDF) traits (+ Clone because that's convenient).
• a type change for the nonce field of EncryptedSecretShare: it now is a Nonce<C::Cipher> which conveniently wraps around a GenericArray to give some guarantees on the expected underlying length, and remove the current hardcoded nonce length.
• the default Cipher for testing is now Aes128Gcm. The rationale is that
  • following a bump of the aes crate from v0.7 to v0.8, there's been a big refactor removing among others the ctr mode
  • gcm is much better than ctr

Note that I didn't go for the aes-gcm-siv crate as:

• the available structure implementing the Ciphersuite trait is, as mentioned, only for testing purposes
• we don't really care about nonce reuse at this level, as even if Aes128Gcm was used as internal cipher in production, we'd need over 4 billion encryption over the same initial DH key to have problems...

Note that because of the new C::Cipher type, and the use of Aes128Gcm in testing, I had to manually implement several of the previously derived traits for EncryptedSecretShare. The nonce field for (de)serialization requires collecting, though shouldn't be a bottleneck hence I left it as a Vec.

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (a9c3b0c) 78.39% compared to head (e9b3dd2) 78.04%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   78.39%   78.04%   -0.36%     
==========================================
  Files          14       14              
  Lines         884      929      +45     
==========================================
+ Hits          693      725      +32     
- Misses        191      204      +13     

Files	Coverage Δ
src/ciphersuite.rs	100.00% <ø> (ø)
src/dkg/complaint.rs	98.14% <ø> (ø)
src/dkg/key_generation.rs	79.43% <ø> (-3.58%)	⬇️
src/lib.rs	100.00% <ø> (ø)
src/error.rs	0.00% <0.00%> (ø)
src/dkg/secret_share.rs	87.28% <81.25%> (+2.87%)	⬆️

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[4l0n50]

Looks good to me