epoch_stake doesn't include entries without funds

[kderme]

If an address is delegated but owns no ada it's not included in epoch_stake. We may want to change that for the next major release 14

While this will lead to more entries, this one reduces them #2018

[rdlrt]

this one reduces them

Initial thought w/o checking stats yet: That's only valid for dApps/wallets, doesnt help explorers/query layers, for which - this will likely increase cost permanently (as number of empty registered stake address would've - and will contine to - increase over the years.

As against that a stake address delegated to a pool but missing in epoch_stake can be easily coalesced to 0 at SQL layer (like it is being done now)