Add pagination support for AllValidatorsQuery

[alpe]

The AllValidatorsQuery queries the active set only (in wasmd). But it may become a more expensive query with a big set as seen on evmos testnet (300 validators)

The SDK provides a pagination object. But for an efficient query we should restrict this to:

• key
• limit

[ethanfrey]

Hmmm... this is part of the CosmWasm API. We stabilised and tagged 1.0 API now. Guess we have to live with it, or find some non-breaking way to move forward. That will involve coordination of cosmwasm-std and wasmd....

[webmaster128]

Where does this cause problems?

Breaking down one query into multiple will only be more expensive because you still need to serialize and deserialize every validator entry. It might save a bit of memory. So the real benefit would be for contracts that only want to query a subset of validators.