Add exported Tries methods to set tries

- `SetEmptyTrie` to set an empty trie without taking a state version argument
- `SetTrie` to change `NewTries` constructor to NOT take a trie as input

dot/state/tries.go

@@ -53,6 +53,14 @@ func NewTries(t *trie.Trie) (tries *Tries) {
 	}
 }
 
+func (t *Tries) SetEmptyTrie() {
+	t.softSet(trie.EmptyHash, trie.NewEmptyTrie())
+}
+
+func (t *Tries) SetTrie(trie *trie.Trie) {
+	t.softSet(trie.MustHash(), trie)
+}
+
 // softSet sets the given trie at the given root hash
 // in the memory map only if it is not already set.
 func (t *Tries) softSet(root common.Hash, trie *trie.Trie) {

dot/state/tries_test.go

@@ -32,6 +32,49 @@ func Test_NewTries(t *testing.T) {
 	assert.Equal(t, expectedTries, rootToTrie)
 }
 
+func Test_Tries_SetEmptyTrie(t *testing.T) {
+	t.Parallel()
+
+	tr := trie.NewTrie(&node.Node{Key: []byte{1}})
+
+	tries := NewTries(tr)
+	tries.SetEmptyTrie()
+
+	expectedTries := &Tries{
+		rootToTrie: map[common.Hash]*trie.Trie{
+			tr.MustHash():  tr,
+			trie.EmptyHash: trie.NewEmptyTrie(),
+		},
+		triesGauge:    triesGauge,
+		setCounter:    setCounter,
+		deleteCounter: deleteCounter,
+	}
+
+	assert.Equal(t, expectedTries, tries)
+}
+
+func Test_Tries_SetTrie(t *testing.T) {
+	t.Parallel()
+
+	trieA := trie.NewTrie(&node.Node{Key: []byte{1}})
+	trieB := trie.NewTrie(&node.Node{Key: []byte{2}})
+
+	tries := NewTries(trieA)
+	tries.SetTrie(trieB)
+
+	expectedTries := &Tries{
+		rootToTrie: map[common.Hash]*trie.Trie{
+			trieA.MustHash(): trieA,
+			trieB.MustHash(): trieB,
+		},
+		triesGauge:    triesGauge,
+		setCounter:    setCounter,
+		deleteCounter: deleteCounter,
+	}
+
+	assert.Equal(t, expectedTries, tries)
+}
+
 //go:generate mockgen -destination=mock_gauge_test.go -package $GOPACKAGE github.com/prometheus/client_golang/prometheus Gauge
 //go:generate mockgen -destination=mock_counter_test.go -package $GOPACKAGE github.com/prometheus/client_golang/prometheus Counter