Add benchmarks for block validation

[CjS77]

Add a benchmark test that times some "standard blocks"

• Empty block
• Full block - each transaction having 1 - 5 inputs and 1 - 20 outputs
• One massive coinjoin (~1,000 inputs, 1 output)
• One huge coin split (1 output, ~1,000 outputs)
• An invalid block - invalid proof of work
• An invalid block - kernel signature
• Invalid blocks - invalid UTXO (double spend, and does not exist)
• Invalid block - insufficient difficulty

[willyrgf]

Hi @CjS77, I'm interested in try to solve this issue. There's some time since the last update here. Is this issue still valid?

[stringhandler]

Hi @willyrgf, yep, still valid.