feat: add ChaCha20 crypto transport

[TwoTenPvP]

[TwoTenPvP]

Two things not yet finished:

1. IV and Counter has to be reset for every packet. Otherwise we will get a keystream mismatch when a packet goes out of order or go missing.
2. There is not yet a validation handler for certificates. All certificates are blindly just "accepted".

Both these things should be fixed before we merge this. But it's a good starting point for crypto. I will get to this once I have time. Just thought it still might be useful as a PR in the meantime.

[TwoTenPvP]

Counter synchronization is now implemeneted. You can have anywhere between 64-128 blocks of loss or reordering before things break.

This could be massively improved by using some of the first header byte to store a slightly larger counter (just a few bits would make a huge difference). This however requires custom int rollover so will have to be future developments.

A cert handler is also implemented and required when using signed handshakes.

[LukeStampfli]

Had to retarget this at main so that we can delete the master branch.

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