Consider refactoring `upgrade_to_electra`

Line 152 in 477fa0e

exit_balance_to_consume=get_activation_exit_churn_limit(pre),

The exit_balance_to_consume and the consolidation_balance_to_consume in upgrade_to_electra both currently take a deneb state but as written they are electra functions so expect an electra state.

The functions currently do not touch any electra data and so there is no test/build issue, but this is a bit confusing for implementation.

We could initialize these fields as 0 and then compute them on the next line using the post variable (that has the correct type).