trie: separate hashes and committer, collapse on commit

* trie:  make db insert use size instead of full data

* core/state: minor optimization in state onleaf allocation

* trie: implement dedicated committer and hasher

* trie: use dedicated committer/hasher

* trie: linter nitpicks

* core/state, trie: avoid unnecessary storage trie load+commit

* trie: review feedback, mainly docs + minor changes

* trie: start deprecating old hasher

* trie: fix misspell+lint

* trie: deprecate hasher.go, make proof framework use new hasher

* trie: rename pure_committer/hasher to committer/hasher

* trie, core/state: fix review concerns

* trie: more review concerns

* trie: make commit collapse into hashnode, don't touch dirtyness

* trie: goimports fixes

* trie: remove panics

trie/proof.go

@@ -64,26 +64,24 @@ func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) e
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}
 	}
-	hasher := newHasher(nil)
+	hasher := newHasher()
 	defer returnHasherToPool(hasher)
 
 	for i, n := range nodes {
-		// Don't bother checking for errors here since hasher panics
-		// if encoding doesn't work and we're not writing to any database.
-		n, _, _ = hasher.hashChildren(n, nil)
-		hn, _ := hasher.store(n, nil, false)
+		if fromLevel > 0 {
+			fromLevel--
+			continue
+		}
+		var hn node
+		n, hn = hasher.proofHash(n)
 		if hash, ok := hn.(hashNode); ok || i == 0 {
 			// If the node's database encoding is a hash (or is the
 			// root node), it becomes a proof element.
-			if fromLevel > 0 {
-				fromLevel--
-			} else {
-				enc, _ := rlp.EncodeToBytes(n)
-				if !ok {
-					hash = hasher.makeHashNode(enc)
-				}
-				proofDb.Put(hash, enc)
+			enc, _ := rlp.EncodeToBytes(n)
+			if !ok {
+				hash = hasher.hashData(enc)
 			}
+			proofDb.Put(hash, enc)
 		}
 	}
 	return nil