trie: use common.Hash as the key in secKeyCache map

[mask-pp]

Simplify secKeyCache to avoid unnecessary transfers among []byte, string and common.Hash.

[MariusVanDerWijden]

Could you show that there is a benefit to this with a benchmark?

[mask-pp]

Could you show that there is a benefit to this with a benchmark?

Ok, I'll add a benchmark test case to show the difference.

[mask-pp]

Could you show that there is a benefit to this with a benchmark?

This is the benchmark result:

BenchmarkSecKeyCache/string_key
BenchmarkSecKeyCache/string_key-12         	51602098	        22.25 ns/op
BenchmarkSecKeyCache/hash_key
BenchmarkSecKeyCache/hash_key-12           	96151920	        12.39 ns/op

This is the test case:

func BenchmarkSecKeyCache(b *testing.B) {
	values := make(map[int]common.Hash) // collect test data
	for i := range b.N {
		data := common.FromHex(fmt.Sprintf("%x", i))
		hk := common.BytesToHash(data)
		values[i] = hk
	}

	valuesStr := make(map[string][]byte)
	b.Run("string_key", func(b *testing.B) {
		for i := range b.N {
			key := values[i]
			valuesStr[string(key[:])] = nil // Simulate the operation before modification.
		}
	})

	valuesHash := make(map[common.Hash][]byte)
	b.Run("hash_key", func(b *testing.B) {
		for i := range b.N {
			key := values[i]
			valuesHash[key] = nil // Simulate the operation after modification.
		}
	})
}

[mask-pp]

Could you show that there is a benefit to this with a benchmark?

This change can also eliminate the map conversion:

[rjl493456442]

SGTM