Implement exporting data to era1 files in our eth_data_exporter tool and use it to for Portal injection

[kdeme]

If we have https://github.com/status-im/nimbus-eth1/issues/1940 implemented, a first step should be to export this via this tool and then to adjust the current Fluffy historyPropagateXXX calls to use these files.

That way we can create era1 files and use them for pre-merge data injection into Portal history network.