Describe the feature

once we have #15371 we need a way to generate an era store with the current database.

for this we simply need to read all the tables and pipe these into an era writer.

TODO

• add new command and impl for era export <>

Additional context

This approach can be similar to #15737
but we only need a regular provider that reads block data and writes them to an era file

ref: https://github.com/ethereum/go-ethereum/blob/9b4eab6a29704f55fa7b4b92e296094f0dbcee22/cmd/utils/cmd.go#L403-L405

this can accept a config struct for first,last,path etc.
in a separate step we can add a cli command that then invokes this