Light Client integration testing with Cosmos Hub

[thanethomson]

We should be automatically testing the Light Client against a live network on a regular basis, and it probably makes the most sense to test against the Cosmos Hub.

To do this we have 2 options:

1. Run a daily scheduled job in CI to test the Light Node against the Hub. This could start at some arbitrary height and sync up to the latest.
2. Run a long-running process somewhere that continuously synchronizes with multiple validators across the Hub.

Option (2) starts leaning more towards running a "production" Light Client that's continuously checking for evidence of malfeasance, so it's probably not the best course of action to address our immediate concerns, but is definitely something we should investigate.

As such, option (1) would probably be the best course of action here.

Both options will effectively act as integration tests for #834 and #842.

What's the definition of "done" for this issue?

When we have a daily scheduled job running the Light Client in some form (e.g. the Light Node) against the Cosmos Hub, sync'ing from some arbitrary height (perhaps the latest minus 20 blocks?) up to the latest block.