x/stake: Add another function for UpdateValidator if cliff validator doesn't exist

[ValarDragon]

Summary

I feel like we can significantly improve the code clarity for UpdateValidator if we separate concerns there, and have a different method if the cliff validator already exists, and doesn't already exist. This is evidenced by there being 3 "if cliff val exists" calls in the function.

/cc @rigelrozanski @cwgoes @alexanderbez

[alexanderbez]

Agreed this could be improved a bit. ref: #1923

[rigelrozanski]

good idea!

[cwgoes]

Concept ACK. Maybe there are other places in staking we could similarly simplify.

[rigelrozanski]

Possibly superseded issue if we remove cliff validator all-together....

[cwgoes]

Possibly superseded issue if we remove cliff validator all-together....

Maybe, but I think the cliff validator logic is a substantive performance improvement for the majority of likely real calls of UpdateValidator.

[rigelrozanski]

@cwgoes let's discuss this more - of course we want the performance - however I think there may be other ways which we could get (nearly) the same performance increase without having all the headache and code complexity of the cliff validator - see thoughts here: #2312

Let's talk about it in today's call however

[ValarDragon]

Closing in favor of #2312, this becomes kind of irrelevant since we no longer have a reserved "cliff validator" seat, its just the 100th element of the arr, and we're switching to the end-block stuff.