trie: polishes to trie committer (#21351)

* trie: update tests to check commit integrity

* trie: polish committer

* trie: fix typo

* trie: remove hasvalue notion

According to the benchmarks, type assertion between the pointer and
interface is extremely fast.

BenchmarkIntmethod-12           1000000000               1.91 ns/op
BenchmarkInterface-12           1000000000               2.13 ns/op
BenchmarkTypeSwitch-12          1000000000               1.81 ns/op
BenchmarkTypeAssertion-12       2000000000               1.78 ns/op

So the overhead for asserting whether the shortnode has "valuenode"
child is super tiny. No necessary to have another field.

* trie: linter nitpicks

Co-authored-by: Martin Holst Swende <martin@swende.se>