Reconsider gas limit for block proposals

from Iddo

One non-trivial part is to set the total gas for the proposals according to the UCB gas limit that wr want, because the proposals get merged, and the UCB gas is what we care about the most because it stays forever.
For example if we we want the UCB gas to be 500k, then we shouldn’t say that each proposal (with single eligibility) is 500k/50==10k because the final gad after merging will be much less than 500k, it might even be just 10k when all the proposals are the same. We can assume something around 500k*ln(500k)/50==62k as discussed at section 5.4 of Tortoise and Hares Consensus: the Meshcash Framework for Incentive-Compatible, Scalable Cryptocurrencies but if there are many malicious proposals there the UCB size will be bigger than we want. Another thing is that if we set say 62k per proposal and the proposed has say 10 eligibilities and he’s allowed to proposal of 620k then that’s bad news if he’s malicious (and even if he’s not malicious then it might not be nice to handle a burst of large proposals with 620k gas etc.), so we might also prefers a non-trivial max gas formula for a proposer with multiple eligibilities (non-linear formula that diminishes).