Compile time regression due to added X25519MLKEM768 support

[CathalMullan]

Just though I'd highlight that the added libcrux-ml-kem dependency in rustls-graviola has resulted in much longer compile times.

On my local M1 Macbook:

> git checkout v/0.2.1
> cargo clean
> cargo build --release --package rustls-graviola
    ...
    Finished `release` profile [optimized] target(s) in 6.60s

> git checkout v/0.3.1
> cargo clean
> cargo build --release --package rustls-graviola
    ...
    Finished `release` profile [optimized] target(s) in 22.44s

[ctz]

Yep, will be working on this once the verified assembly for this lands in s2n-bignum.

[alex]

Does working on this mean basically having graviola have its own MLKEM impl based on that assembly?

[ctz]

Yes. Taking the libcrux-ml-kem dependency allows rustls-graviola to have good defaults in the meantime.

[alex]

For sure makes sense, was just curious. Thanks!