Cosmos-sdk: x/stake: Keeper - Improve Coverage, API and Documentation

[alexanderbez]

Currently the coverage for the keeper package in the stake module is ~71.6%. Things I noticed that I think could be improved:

• Increasing unit test coverage (e.g. UpdateBondedValidatorsFull, GetAllValidators, GetValidators)
• Improved/added documentation to some methods/functions
• Cleaning up some APIs (e.g. a lot of methods can probably be condensed and GetValidatorsByPower is not indicative that it returns bonded validators).

I'd be happy to do all of the above.

/cc @cwgoes @rigelrozanski

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[cwgoes]

All of those sound like great ideas. I think it's also worth seeing if we can reorganize or split up several of the complex validator update functions to clarify preconditions and postconditions for various intermediary states - that should be done before unit tests.

[alexanderbez]

Yes x100 @cwgoes 👍

[rigelrozanski]

Another thing we should test out a bunch of comparisons for the power key https://github.com/cosmos/cosmos-sdk/blob/8053d7fdf509cb859a00be0166c502a182dc4a80/x/stake/keeper/key.go#L70

[cwgoes]

I think this has either been done or superseded by more recent issues, although more unit tests are always good!