saturation metric fix

[gabririgo]

the saturation metric uses

getGlobalStakeByStatus("delegated")

which is different from the metric used for staking rewards calculations (totalWeightedStake), which is

aggregatedStatsByEpoch(current epoch)[3]

I believe the choice was made in order to display saturation as a projective measure for the upcoming epoch, taking into account new stake which has occurred before the start of the next epoch.

There's tradeoffs in either solution, and I think it's worth a discussion to understand whether the issue is relevant. I am happy to close the issue should we deem the projective measure, though incorrect, is better from a users' perspective.