Add more debugging information about blocks produced

[matthewdarwin]

Original issue: EOSIO/eos#8477

To ease troubleshooting it would be very helpful to log more information about the size of the block in nodeos standard output

Today it looks like this:

Received block 2804890f34cb6cd3... #101125076 @ 2020-01-20T16:11:58.500 signed by eoseouldotio [trxs: 8, lib: 101124757, conf: 0, latency: 265 ms]

Request is to add things like:

• size of the block (number of bytes) as seen by the producer in question
• amount of CPU used by the producer in question

If computing this information will take additional CPU, the probably it should be optionally controlled by either a configuration or logging option.