Reduce CosmWasm gas cost by a factor of 1000

[webmaster128]

We have been warned that gas consumption might hit the uint64 limit and lead to overflows or crashes. In https://github.com/CosmWasm/cosmwasm/pull/1222/files we documented why this cannot easily happen.

However, the gas values in CosmWasm are incredibly high. Each Wasm operation costs 150_000 gas and the Cosmos SDK / CosmWasm gas multiplier is at 140_000_000.

Reducing the factor allows us to get an additional safety margin of 1000x while preserving the necessary granularity level. This additional safety can be useful in the event of mispricing or execution times much larger than typical block times we see today.

	CosmWasm 1.x	CosmWasm 2.x
Cost target	1 Teragas/millisecond	1 Teragas/second
Exceeds uint64 range after	5 hours	5124 hours (213 days)
Cost per Wasm op	150_000	150
Multiplier	140_000_000	140_000