multi-test: ensure event handling matches wasmd 0.18 implementation

[ethanfrey]

There is a lot of logic, for renames and for rejecting that is present here:

https://github.com/CosmWasm/wasmd/blob/master/x/wasm/keeper/events.go
(and include return error where the FIXME is, rather than continue)

We should implement the equivalent in multi-test

BLOCKED: Let us merge CosmWasm/wasmd#440 first so we have final event status