set up local-interchain builder suite

[bekauz]

part of #167

before getting into actual e2e tests we should set up a builder suite for the local-interchaintest.

we should support (but not limit ourselves to):

• arbitrary number of chains, allowing custom ibctest.ChainSpec configurations
• arbitrary number of relayers, supporting both CosmosRly and Hermes
• links between chains, supporting ibctest.InterchainLink, ibctest.ProviderConsumerLink, and polytone connections

note: this issue is about the suite to be used for the actual unit tests, not the local-ic json configuration