SCCP-260: Update Synthetix Liquidation Parameters

Simple Summary

This SCCP proposes to implement the following:

liquidationRatio is the ratio below which stakers can be flagged for liquidation, after the liquidationDelay of 8 hours,the flagged staker is liquidated.
liquidationPenalty is the penalty paid to other stakers who take on the debt of the liquidated account.
selfLiquidationPenalty is the penalty paid to other stakers, when a staker liquidates his debt to the target collateralization ratio.

The motivation for pushing up these parameters are as follows:

1-Year short funding rates on SNX has been been historically around 75%. If a staker who earns liquidation rewards and wants to hedge his escrow, he can't sell it and has to pay an 75% funding rate. So a penalty of 75% would bring the net present value of the debt assumed in line with that of liquidation rewards.
Increases the incentive on stakers to repay their debt.
Increases the incentive for stakers to bring additional capital into the system to take on the liquidated snx of fallen brothers.