use collections for the x/btcstkconsumer and x/zoneconcierge modules #423
Description
Cosmos SDK v0.50 has introduces collections library for handling KV stores. It provides more friendly interfaces compared to the old ones (example).
Since x/btcstkconsumer and x/zoneconcierge are not on mainnet yet, we can take the opportunity to leverage collections library for KV stores in the two modules.