Backport: refactor block log

[vladtr]

There are some really good bits and pieces for backport here:

EOSIO/eos#9019

There is a fix/update to it here:

EOSIO/eos#10711

[oschwaldp-oci]

Blocklog refactor related. May not plan to backport this due to differences with blocklog changes, but instead work it when backlog path forward decided.