feat(tokenomics): charge more fees for blocks that are harder to prove

[dantaik]

Previously, when blocks are proven after 1.25*avgProofTime, we mint extra tokens to incentivize the provers, but the blocks' proposers get away without paying extra fees. This may open a door for DOS attack -- the proposers may simply create certain transactions that are harder to prove.

This PR enable the protocol to charge up to 25% additional fees -- 125% of the original proposer fees are burnt initially (100% is the fee, and 25% is called the deposit), then based on the tRef value in the whitepaper, we mint back [0-100%] of the deposit back to the proposer. If tRef == 0, we mint back all deposit, if tRef == 10000, we mint back no deposit to the proposer.

[codecov]

Codecov Report

Merging #351 (895aeee) into implement-tokenomics-v1_pr (597b72c) will decrease coverage by 2.16%.
The diff coverage is 0.00%.

@@                      Coverage Diff                       @@
##           implement-tokenomics-v1_pr     #351      +/-   ##
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- Coverage                       63.68%   61.51%   -2.17%     
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  Files                              88       88              
  Lines                            2489     2580      +91     
  Branches                          283      296      +13     
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+ Hits                             1585     1587       +2     
- Misses                            831      920      +89     
  Partials                           73       73              

Flag	Coverage Δ		*Carryforward flag
protocol	55.48% <0.00%> (-3.38%)	⬇️
relayer	68.80% <ø> (-0.13%)	⬇️	Carriedforward from 36033be
ui	100.00% <ø> (ø)		Carriedforward from 36033be

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
packages/protocol/contracts/L1/LibData.sol	21.42% <ø> (ø)
packages/protocol/contracts/L1/TaikoL1.sol	20.00% <0.00%> (-2.23%)	⬇️
packages/protocol/contracts/L1/v1/V1Proposing.sol	0.00% <0.00%> (ø)
packages/protocol/contracts/L1/v1/V1Utils.sol	0.00% <0.00%> (ø)
packages/protocol/contracts/L1/v1/V1Verifying.sol	13.69% <0.00%> (ø)
packages/relayer/http/server.go	93.15% <0.00%> (-2.74%)	⬇️
packages/protocol/contracts/L1/TkoToken.sol	84.21% <0.00%> (ø)
packages/protocol/contracts/L2/V1TaikoL2.sol	56.81% <0.00%> (ø)
... and 17 more

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[Brechtpd]

Previously, when blocks are proven after 1.25*avgProofTime, we mint extra tokens to incentivize the provers, but the blocks' proposers get away without paying extra fees. This may open a door for DOS attack -- the proposers may simply create certain transactions that are harder to prove.

If the average price increases after the protocol notices the prover fee it charges proposers is too low, and the amount of blocks that can be submitted before this happens is limited, is there a way for proposers to abuse the system? For the proposers the only thing that would matter is the gas cost. They could submit a lot of transactions that are more expensive to prove when the prover fee is "low", which will increase the prover fee eventually. They could then submit transactions that are cheap to prove to get the prover fee down again. I don't think there is anything wrong with that, it's just that the transactions fees for the second part will be higher than necessary (but the transaction fees will be lower than the transaction fees in the first part). Transaction fees will be fluctuating a lot anyway so I don't really see a real problem with that. For now I can't really see a way the system could be abused but I could be missing something.

This PR enable the protocol to charge up to 25% additional fees -- 125% of the original proposer fees are burnt initially (100% is the fee, and 25% is called the deposit), then based on the tRef value in the whitepaper, we mint back [0-100%] of the deposit back to the proposer. If tRef == 0, we mint back all deposit, if tRef == 10000, we mint back no deposit to the proposer.

I do want to stress that this is a big change to how the fee market will work, and will put potentially a lot of complexity on the proposers to create profitable blocks. It could introduce a DOS vector on proposers or increase transaction fees for users if having to calculate the costs by having to actually execute the transactions is a hard problem to solve well. Keeping prover fees linked to gas cost will allow us to use any existing fee market/MEV code pretty much out of the box, if we change that we will be forced to support modified versions that are specifically made for Taiko.