Use a message-based system for voyager (#635)

Lots of big changes! (Apologies for the 100k+ diff)

# Additions

- Move chain definitions into a standalone crate so they can be consumed
by hubble (eventually)

# Major changes (outside of voyager)

## `unionlabs`

- Make IBC message types generic over some of their field types (mainly
`Height`, `ClientId`, and `ClientType`)

- This allows for more type checking within the new relayer code -
instead of `MsgConnectionOpenTry`, you have the following:

    ```rust
    MsgConnectionOpenTry<
        ClientStateOf<L::HostChain>,
        L::ClientId,
        <L::Counterparty as LightClient>::ClientId,
        HeightOf<ChainOf<L::Counterparty>>,
        HeightOf<ChainOf<L>>,
    >
    ```

    Requiring that the values passed in are from the correct source.