block time not stable

[FlorianHuc]

Besu is configured with a block time of 4s, but more than 4s ellapse between two blocks. It seems that the timer for block creation does not start right after the previous block was produced as shown in these logs:

[fab-10]

Which is the value of poa-block-txs-selection-max-time?

We also need to review if there were txs to be included in a block, since we skip producing empty blocks

[fab-10]

Evaluate the correlation between the increase of tx-pool-max-prioritized to 32000 and this.

Green is 16k, blue is 24k, yellow is 32k