Param proposals, balance inquiries, and IBC transfer error handling

[bigs]

Some things old, some things new...

New Features

In writing some tests involving the impact of some module params on IBC transfers, we added a few new methods to the CosmosChain.

ParamChangeProposal

Submits a parameter change proposal to the gov module. For simplicity's sake (and since a majority of the ChainNode methods leverage the cosmos-sdk command-line interface to interact with the chain anyway) we borrowed our argument type directly from the params module's client utils module. Fairly straightforward and exposed at the CosmosChain level as well.

AllBalances

Uses the gRPC client (as GetBalance does) to query for all of the coins held by an account address. Almost a carbon-copy of GetBalance.

Updated Features

After encountering some unexpected behaviors in our tests, we found what we believe to be a bug in the SendIBCTransfer command.

SendIBCTransfer response code handling

We noticed that SendIBCTransfer does not inspect the transaction response's Code before populating the Tx object and returning it. This leads to situations where a transaction goes through unsuccessfully but the test author has no way of knowing this, since the ibc.Tx object doesn't include the response code. We thought it more correct to return an error in this case.

Our use case here was disabling a token from being sendable in the bank module (via params, hence the params proposal.) What we found was that even though we were getting a response code 7 indicating that the transfer was unsuccessful (as we expected), from our test's perspective everything was going along well.

Edit: We also added a helper function for writing files into the docker volume, since we saw the same pattern duplicated many times over.

[agouin]

Thank you! Looks great