Adjusting Polkadot's Ideal Staking Rate Calculation

[jonas]

Hi Kian

Thanks for the feedback.

Yes, this change requires us to be quick. I talked with @gpestana who can implement the code change. I also consulted @bkchr, who expects that we can make it in time. He also told me, that we only require to change the runtime configuration (in contrast to the runtime crate), so it should be quick.

@kianenigma

Learning from the pains of the current mechanism, this future inflation rate should be a storage item such that it can be tweaked easier.

This will be part of this change.