Choose a uniform power calculation method

[cwgoes]

Either full sdk.Decimal precision or limited Tendermint power precision, and use that uniformly - in fee distribution, staking, power ranking, etc.

ref https://github.com/cosmos/cosmos-sdk/pull/2508/files#r225712555
ref #2439 (comment)

Maybe we should have an even higher threshold for delegation/undelegation/redelegation, in part to mitigate fee distribution DoS risk.

cc @ValarDragon

[ValarDragon]

This seems good to me. (Presuming we're going with the fixed "Unit" approach, which will be specified by a governance change-able parameter, and is a power of 2. All relevant stake will be determined in integer quantities of Unit, with the integer not exceeding 2**63. (Or perhaps 2**51))

We do need to note and have a plan for the complications which will arise when upgrading the threshold, and how we would have to correctly reward the rewards from delegations/undelegations etc. along with keeping the correct amount slashable.

I do think this is a good idea. Then we can get faster computations on the int64's + less on-chain data usage.

[rigelrozanski]

Yeah I could see us migrating to int's all the way around for the power representation of a validator however we will still need to use the decimals for a wide variety of mechanism calculations, we just want to limit its use in the final results (aka withdrawn fees, withdrawn inflation, etc) - like there are many circumstances where folks are continuously accumulating "fractions" of rewards which really add up over blocks - just need to have consideration for this and use decimal in those place appropriately

[jackzampolin]

This discussion carried over from: #2439

[rigelrozanski]

At @cwgoes were you planning on doing this soon? was also on my roster but if you want to take on that's also dope.

I do not see why GoS should require blocking on this.

[cwgoes]

@rigelrozanski At first I thought this was necessary for GoS but upon reflection decided that this method would be annoying since we would have to change the unit constant mid-Game. For now I think we'll just decrease the inflation slightly so we won't hit the int64 limit - but we should definitely still do this after GoS. Glad to pick it up but if you want to do it that's fine too.