Query without gas metering

[assafmo]

This PR increases query performance by about 25% (1.25x).

A large query	Time (s)
Without gas metering	41.273849005
With gas metering	52.79072004

Notes:

• This cannot be released as a non-breaking v1.3.x version. A contract can use query_chain() to force different gas behavior from current v1.3.x versions and thus break consensus.
• TODO: Test like hell that this cannot happen inside a tx.
• TODO: On CosmWasm v1 make sure that it's not gameable using StaregateQuery.