Update light client if close to expiration

[boojamya]

The goal of this PR is to ensure light clients don’t expire on low trafficked paths where MsgUpdateClient isn’t being sent regularly.

The assembleAndSendMessages function gets called on every block that has available signals to process. This is where we put a check to see if the light client is close to being expired.
We update the light client if it has less than 1/3 of its trusting period left.

We get the trusting period of the client when we create a new cosmos_chain_processor and cache this info so it is not need to make this call every block.
I believe all of the client state info, including the trusting period, will be updated in the relayers cache every time it handles relevant transaction messages

Question:

• Is this OK to build into the overall relayer functionality? Will this effect non-cosmos based chains implementation of the relayer?

Todo:

• It would be nice to wire up a test in IBCtest to ensure this works properly.

Props to @agouin for taking the time to run through this with me.

Closes: #853

[boojamya]

Stale. Closing in favor of: #1008