trie: reduce allocs in insertPreimage (#21261)

trie/database.go

@@ -349,14 +349,15 @@ func (db *Database) insert(hash common.Hash, size int, node node) {
 }
 
 // insertPreimage writes a new trie node pre-image to the memory database if it's
-// yet unknown. The method will make a copy of the slice.
+// yet unknown. The method will NOT make a copy of the slice,
+// only use if the preimage will NOT be changed later on.
 //
 // Note, this method assumes that the database's lock is held!
 func (db *Database) insertPreimage(hash common.Hash, preimage []byte) {
 	if _, ok := db.preimages[hash]; ok {
 		return
 	}
-	db.preimages[hash] = common.CopyBytes(preimage)
+	db.preimages[hash] = preimage
 	db.preimagesSize += common.StorageSize(common.HashLength + len(preimage))
 }