Experiment: State queries vs event subscription

[matthiasgeihs]

Background:
A common way to read state from a CosmWasm contract is to use query messages. On other blockchains, however, a more common pattern keeping up to date with contract state is using event subscriptions.

Idea:
Recently, CosmWasm has also provided documentation of their event system. We could investigate and try out what benefits and drawbacks using event subscription over state queries has in the context of the Perun CosmWasm backend.