Experiment with some transaction protocol changes for better performance

[lrubasze]

This is to find and assess some short-term solutions before Streamlined Block Production is introduced.

Ideas to expore:

• Tweak transaction protocol related constants
  (more details here: DNM/WIP transaction protocol related consts bumped #7804)
• Async notification sending
  poc here: poc: async backpressure for transaction notifications #9296
• Batching transactions into a notification
  poc here: [DNM] net/transactions: Optimize the protocol to enhance transaction throughput #7828
  It was decided that this approach will not be chased, but we can still measure it and compare it with others.