Reward anti-whaling

[barnabee]

Currently rewards suffer do not work as intended when applied to a range of markets, such as all markets with the same settlement assst.

Users on long tail markets receive almost no rewards compared to the most popular markets where there's a orders of magnitude difference in the volume between the most and least popular markets. This is at odds with the fact that the bigger markets generate more fees and profits for MMs, and so are less in need of incnetivisation. The result is rewards have to be manually targeted to smaller markets if the aim is to help them grow.

To fix this, an "anti-whaling" featujre similar in spirit (and likely in design, too) to the one that has helped to successfully keep VEGA delegation well distributed will be introduced to the protocol. This will put a cap on the share of rewards distributed for activity on each market relative to the equal fair share.

For example: if there are 10 markets, the "fair" share for each would be 10% of the rewards per market. Depending on the volume on each, with no anti-whaling, one market mayh get 90% of the rewards. Anti-whaling would allow the amount to be capped to some multiple of this fair share number, e.g. 2x would mean a larger market could get up to 20% of the rewards, or 1x would distribute the rewards eqaually between markets in all cases.

This must be optional, so that a reward can be distributed as they are now if desired.

[davidsiska-vega]

Maybe we don't need anti-whaling IF scaling #2318 is up and running.