Trie parallel hashing

[hqjang-pepper]

Proposed changes

This is a follow-up PR of #1656, should be merged after #1656

• Trie starts to count when it tries to update/delete nodes
• when unhashed >= 100, fullNode hashing operation is parallelized
• Should be merged after Seperate trie commit and hash #1656
• related ethereum PR : Parallel hashing ethereum/go-ethereum#20488

Types of changes

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• Bugfix
• New feature or enhancement
• Others

Checklist

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• I have read the CONTRIBUTING GUIDELINES doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes ($ make test)
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

• Please leave the issue numbers or links related to this PR here.

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[hqjang-pepper]

before & after applying #1659 + #1656

• Hash

before
BenchmarkHashFixedSize
BenchmarkHashFixedSize/10
BenchmarkHashFixedSize/10-10 	           27930	     42784 ns/op	   14004 B/op	     157 allocs/op
BenchmarkHashFixedSize/100
BenchmarkHashFixedSize/100-10         	   10000	    100930 ns/op	   65665 B/op	     777 allocs/op
BenchmarkHashFixedSize/1K
BenchmarkHashFixedSize/1K-10          	    1232	    982107 ns/op	  657792 B/op	    7784 allocs/op
BenchmarkHashFixedSize/10K
BenchmarkHashFixedSize/10K-10         	     277	   4412435 ns/op	 6906100 B/op	   79662 allocs/op
BenchmarkHashFixedSize/100K
BenchmarkHashFixedSize/100K-10        	      30	  40766426 ns/op	68241484 B/op	  794507 allocs/op

after 
BenchmarkHashFixedSize
BenchmarkHashFixedSize/10
BenchmarkHashFixedSize/10-10 	           35845	     32955 ns/op	   12054 B/op	     149 allocs/op
BenchmarkHashFixedSize/100
BenchmarkHashFixedSize/100-10         	   10000	    101520 ns/op	   58953 B/op	     740 allocs/op
BenchmarkHashFixedSize/1K
BenchmarkHashFixedSize/1K-10          	    1267	    930975 ns/op	  598084 B/op	    7444 allocs/op
BenchmarkHashFixedSize/10K
BenchmarkHashFixedSize/10K-10         	     290	   4117625 ns/op	 6323543 B/op	   77091 allocs/op
BenchmarkHashFixedSize/100K
BenchmarkHashFixedSize/100K-10        	      27	  37786035 ns/op	62431504 B/op	  767766 allocs/op

• Commit

Before
BenchmarkCommitAfterHashFixedSize
BenchmarkCommitAfterHashFixedSize/10
BenchmarkCommitAfterHashFixedSize/10-10 	           30988	     38790 ns/op	   36083 B/op	     208 allocs/op
BenchmarkCommitAfterHashFixedSize/100
BenchmarkCommitAfterHashFixedSize/100-10         	    8286	    145892 ns/op	  174370 B/op	    1022 allocs/op
BenchmarkCommitAfterHashFixedSize/1K
BenchmarkCommitAfterHashFixedSize/1K-10          	     828	   1485660 ns/op	 1701478 B/op	   10143 allocs/op
BenchmarkCommitAfterHashFixedSize/10K
BenchmarkCommitAfterHashFixedSize/10K-10         	      74	  14636495 ns/op	18696716 B/op	  103985 allocs/op
BenchmarkCommitAfterHashFixedSize/100K
BenchmarkCommitAfterHashFixedSize/100K-10        	       7	 148162095 ns/op	180172019 B/op	 1038887 allocs/op

After
BenchmarkCommitAfterHashFixedSize
BenchmarkCommitAfterHashFixedSize/10
BenchmarkCommitAfterHashFixedSize/10-10 	           60080	     20030 ns/op	   30914 B/op	     189 allocs/op
BenchmarkCommitAfterHashFixedSize/100
BenchmarkCommitAfterHashFixedSize/100-10         	   12500	     96729 ns/op	  151233 B/op	     918 allocs/op
BenchmarkCommitAfterHashFixedSize/1K
BenchmarkCommitAfterHashFixedSize/1K-10          	    1052	   1188825 ns/op	 1473359 B/op	    9108 allocs/op
BenchmarkCommitAfterHashFixedSize/10K
BenchmarkCommitAfterHashFixedSize/10K-10         	      94	  11857340 ns/op	16368251 B/op	   93862 allocs/op
BenchmarkCommitAfterHashFixedSize/100K
BenchmarkCommitAfterHashFixedSize/100K-10        	       9	 121488097 ns/op	157054739 B/op	  937567 allocs/op

[jeongkyun-oh]

In ethereum PR, this line is removed, but not here. Any reason for this?

[hqjang-pepper]

cached.Children[16] = n.Children[16]
you mean this line?
Yeah you are right, ethereum changed this line but I didn't, because changing logic has nothing to do with Children[16], So I didn't change this part

[blukat29]

Replaced by #1840.