Add bufreader example

[nyonson]

Trying to capture just how effective a bufreader is for the BIP-324 protocol. I think this shows that it is usually going to help, probably never hurt.

How it generally looks on my machine:

> cargo run --release --example bufreader --features tokio
    Finished `release` profile [optimized] target(s) in 0.05s
     Running `target/release/examples/bufreader`
Bitcoin Traffic: 100000 total messages, 9940000 bytes
  Without BufReader: 126 ms
  With BufReader:    98 ms
  Improvement:       22.1%
Large Messages: 3000 total messages, 90112000 bytes
  Without BufReader: 234 ms
  With BufReader:    233 ms
  Improvement:       0.1%
Small Messages: 100000 total messages, 300000 bytes
  Without BufReader: 101 ms
  With BufReader:    72 ms
  Improvement:       28.2%

[rustaceanrob]

Is this all local data? Could be useful to see how this looks over traffic with latency in the future. Conceptually makes sense.

[nyonson]

Is this all local data? Could be useful to see how this looks over traffic with latency in the future. Conceptually makes sense.

Yea, kinda hard to measure with so many variables, but this is the "best case" scenario for the buffer where there are a lot of packets sittin in the network socket. I would guess the benefit of the buffer only goes down from here. I'll try to model a more realistic network scenario though.