Cleanup eth_data_exporter and fluffy/eth_data helper modules

[kdeme]

The eth_data_exporter that creates exported Portal data and/or test vectors has grown a bit wild due to the evolution of the many used formats for test vectors and the intermediate data storage formats. New things have been added often without cleanup/removal of the old.

This issue is about working on that cleanup/removal.
In general, we should be using as input as much as possible era and era1 files, and where not possible a beacon REST API / EL JSON RPC API.
As output preferred test vectors in yaml, typically just content_key + content pair, and in some cases something more specific. json can also be still an option, as it is still used and easy convertible to yaml.