Write integration tests for relayer-next CLI

[soareschen]

Summary

The integration test should be similar to the basic transfer test in tools/integration-test/src/tests/next/transfer.rs. The key difference is that instead of running the relayer directly, the relayer should be started from the command line.

Details

• The integration test should test for IBC transfer in both ways, from chain A to chain B, then from chain B to chain A.
• The relayer CLI command is in the form cargo run --bin hermes -- [args].
• The relayer CLI is started as a process similar to the Python command in tools/integration-test/src/tests/python.rs. The command should be run in a separate thread, so that it do not block the test.
• If the CLI is working, the IBC transfer in both directions should succeed.