Update RawQuery return value

[ethanfrey]

It takes a key as input, but returns []struct{Key, Value}. We only seems to use res[0].Value (also in the client)

• Verify if there are any cases where we return multiple models
• Update the RawQuery callback for contracts (tested in reflect_test.go::TestMaskReflectWasmQueries)
• Update the RawQuery call for clients (also rest and cli bindings)
• Update doc strings as needed

[ethanfrey]

Okay, we do need to return []Model for QueryMethodContractStateAll which returns all state.

We do not need to use the same return value for QueryMethodContractStateRaw.

I will maintain the behavior for all, but change it for raw.