refactor(protocol): various changes based on Brecht & Dani's feedback

[dantaik]

Previously

test2/TaikoL1.t.sol:TaikoL1WithConfig contract
Function Name	min	avg	median	max	# calls
proposeBlock	18560	24663	18580	65707	339
proveBlock	56069	64958	56069	132369	339
verifyBlocks	17191	41931	17191	148496	331

Now

test2/TaikoL1.t.sol:TaikoL1WithConfig contract
Function Name	min	avg	median	max	# calls
proposeBlock	19057	29415	19077	88104	309
proveBlock	55834	65888	55834	132234	309
verifyBlocks	14944	16139	15869	79299	301

[codecov]

Codecov Report

Merging #13427 (18c915b) into major_protocol_upgrade_rebase (4ddbd9b) will decrease coverage by 0.26%.
The diff coverage is 0.00%.

❗ Current head 18c915b differs from pull request most recent head 975a53d. Consider uploading reports for the commit 975a53d to get more accurate results

@@                        Coverage Diff                        @@
##           major_protocol_upgrade_rebase   #13427      +/-   ##
=================================================================
- Coverage                          40.07%   39.81%   -0.26%     
=================================================================
  Files                                112      112              
  Lines                               3404     3403       -1     
  Branches                             413      405       -8     
=================================================================
- Hits                                1364     1355       -9     
- Misses                              1952     1960       +8     
  Partials                              88       88              

Flag	Coverage Δ		*Carryforward flag
bridge-ui	94.22% <ø> (-0.44%)	⬇️	Carriedforward from a9365be
protocol	0.00% <0.00%> (ø)
relayer	62.30% <ø> (-0.15%)	⬇️	Carriedforward from a9365be
ui	100.00% <ø> (ø)		Carriedforward from a9365be

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

Impacted Files	Coverage Δ
packages/protocol/contracts/L1/TaikoConfig.sol	0.00% <ø> (ø)
packages/protocol/contracts/L1/TaikoL1.sol	0.00% <0.00%> (ø)
...ckages/protocol/contracts/L1/libs/LibProposing.sol	0.00% <0.00%> (ø)
packages/protocol/contracts/L1/libs/LibProving.sol	0.00% <0.00%> (ø)
...kages/protocol/contracts/L1/libs/LibTokenomics.sol	0.00% <ø> (ø)
packages/protocol/contracts/L1/libs/LibUtils.sol	0.00% <0.00%> (ø)
...ckages/protocol/contracts/L1/libs/LibVerifying.sol	0.00% <0.00%> (ø)
...ackages/protocol/contracts/test/L1/TestTaikoL1.sol	0.00% <0.00%> (ø)
.../contracts/test/L1/TestTaikoL1EnableTokenomics.sol	0.00% <0.00%> (ø)

... and 11 files with indirect coverage changes

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[adaki2004]

I see it as above, dont know in which scenario it could happen.
If fcId == 0, then blk.nextForkChoiceId == 1 -> No proof submitted.
If blk.nextForkChoiceId == 2 a proof is submitted either by an oracle or single prover, but in such case the second proof submitted (when unverified) does not increase blk.nextForkChoiceId above 2.

[dantaik]

• fcId==0 means the fork choice does not exist
• fcId >= blk.nextForkChoiceId shall never happen. I convert it into an assert