refactor(protocol): change TaikoToken's decimals from 18 to 8

[dantaik]

The main objective for such a change is to make sure the current and future max supply can fit in to a uint64 so the protocol code can use one single uint64 to hold any taiko token amount.

type(uint64).max/ (10**18) = 184,467,440,737 which is 184 billion. I don't think our max supply will ever be 10 billion.

test2/TaikoL1.t.sol:TaikoL1WithConfig contract
proposeBlock	18589	28621	18609	85536	309
proveBlock	56012	66066	56012	132412	309
verifyBlocks	14484	15675	15409	76980	301

[codecov]

Codecov Report

Merging #13443 (244be54) into major_protocol_upgrade_rebase (0b8f7fe) will increase coverage by 1.00%.
The diff coverage is 0.00%.

❗ Current head 244be54 differs from pull request most recent head ddf02b4. Consider uploading reports for the commit ddf02b4 to get more accurate results

@@                        Coverage Diff                        @@
##           major_protocol_upgrade_rebase   #13443      +/-   ##
=================================================================
+ Coverage                          39.18%   40.18%   +1.00%     
=================================================================
  Files                                111      112       +1     
  Lines                               3366     3394      +28     
  Branches                             382      411      +29     
=================================================================
+ Hits                                1319     1364      +45     
+ Misses                              1959     1942      -17     
  Partials                              88       88              

Flag	Coverage Δ		*Carryforward flag
bridge-ui	94.66% <ø> (+0.65%)	⬆️	Carriedforward from 2e8b0d3
protocol	0.00% <0.00%> (ø)
relayer	62.45% <ø> (-0.14%)	⬇️	Carriedforward from 2e8b0d3
ui	100.00% <ø> (ø)		Carriedforward from 2e8b0d3

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

Impacted Files	Coverage Δ
packages/protocol/contracts/L1/TaikoL1.sol	0.00% <ø> (ø)
packages/protocol/contracts/L1/TaikoToken.sol	0.00% <0.00%> (ø)
...ckages/protocol/contracts/L1/libs/LibProposing.sol	0.00% <0.00%> (ø)
...kages/protocol/contracts/L1/libs/LibTokenomics.sol	0.00% <0.00%> (ø)
packages/protocol/contracts/L1/libs/LibUtils.sol	0.00% <ø> (ø)
...ckages/protocol/contracts/L1/libs/LibVerifying.sol	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

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