Switch Collator rewards source to Treasury

[lolmcshizz]

Currently collators are paid by freshly minted HDX every block/ period of time - in HDX tokenomics this should continue for ~10 years in total, with several revisions to the amount along the way.

There is an ongoing discussion on Hydration Subsquare to mint the full 6.5B HDX supply to the Treasury (this would include the full amount earmarked for Growth as well as collator rewards) - so that there are no further unlocks, increasing transparency.

In order to ensure that 6.5B remains the total supply for HDX, we'll need to convert collator rewards to being distributed from the Treasury every block instead of fresh minting.