Add delay period to tendermint client

[colin-axner]

Summary

Add a delayPeriod to the tendermint client state

Problem Definition

With eureka, the connection layer is removed entirely. If we want to support the ability for clients to have delay periods to increase security, we should add it to the tendermint client (any other clients which would like to add this feature should also add it)

Proposal

Add the delay period to the tendermint client. Set it to 0 by default (this should allow the client state encoding to remain unchanged for backwards compatibility - soon shouldn't be a consideration with removal of self client/consensus state validation).

In Eureka, setting the client to a non-zero delay period would be no problem and give support for delay periods.

In classic, it would be a problem, only if the two chains haven't updated to: v7.8+, v8.5+, v9+. To remedy and support a removal of the connection layer entirely, we should:

• add ability to modify delay period on a client via gov Add a governance proposal to change client parameters #1171

Thus, if connections have non zero delay periods, gov can choose to update or leave as is for the underlying client before we remove connections and thus create the same fundamental security layer for connections sharing the same client.

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