piggyback on `LogCallback` for default behavior & simpler callback impls

[zeroXbrock]

Is your feature request related to a problem? Please describe.

Currently, to implement a custom callback, you need to replicate the behavior of LogCallback to save txs to the DB, to use for generating chain reports with contender report. There exists a lot of required duplication in callback impls that isn't necessarily obvious to callback developers.

Describe the solution you'd like

Would be nice to generalize the behavior of LogCallback, so that every other callback that's written can implicitly execute the base LogCallback::on_tx_sent & LogCallback::on_batch:sent code, and then their code on top of it.

I'm not sure what this should look like. Looking for design specs.