Hashing Buffers

[macalinao]

Buffers could be hashed on-chain to allow for easier program verification. This would remove the need for someone to download the buffer to verify it.

https://github.com/solana-labs/solana/blob/d3a3a7548c857f26ec2cb10e270da72d373020ec/sdk/src/process_instruction.rs#L107

85 + # bytes compute budget means that we can hash a ~200kb program in one transaction. This is insufficient.

However, we can instead create a sha256 hash of each 128kb sector of the buffer then hash the concatenated hashes.

It may be worth putting this into a separate program in the future, coupling this with a validator system that runs verifiable program builds and attests their hashes on-chain.