Sv2 noise

[Sjors]

This is the first part of the Stratum v2 Template Provider, it introduces the Stratum v2 Noise protocol.

It introduces a CMake build flag -DWITH_SV2 that is ON by default.

The Noise Protocol Framework is defined here: https://noiseprotocol.org/noise.html

It's quite similar to BIP324. The main differences are explained here, including why Stratum v2 can't use BIP234 (yet): https://delvingbitcoin.org/t/stratum-v2-noise-protocol-bip324-nuggets/413

The implementation is based on revision 38, 2018-07-11 (most recent at the time of writing).

The Stratum v2 spec defines the specific choice of ciphers: https://github.com/stratum-mining/sv2-spec/blob/main/04-Protocol-Security.md

This protocol has been implemented in the Stratum Reference Implementation (SRI, using rust-bitcoin). https://github.com/stratum-mining/stratum

It has also been (independently) implemented in BraiinsOS. This part is currently not open source, and it's behind on some recent changes.

The classes in sv2_noise.h attempt to stay close to the paper, whereas the test and fuzzer code borrow heavily from BIP324.

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Moved here from bitcoin#29346.

Followed by #67. Parent PR #68.

Note that this code will most likely not be upstreamed to Bitcoin Core, but instead used to create a standalone c++ application that connects to a running node via an IPC interface. See bitcoin#31098.

[Sjors]

Rebased and applied @stratospher's feedback.

[Sjors]

Added SeedRandomStateForTest(SeedRand::ZEROS);