core/state: fix code existence not marked correctly (#33415)

When iterating over a map with value types in Go, the loop variable is a
copy. In `markCodeExistence`, assigning to `code.exists` modified only
the local copy, not the actual map entry, causing the existence flag to
always remain false.

This resulted in overcounting contract codes in state size statistics,
as codes that already existed in the database were incorrectly counted
as new.

Fix by changing `codes` from `map[common.Address]contractCode` to
`map[common.Address]*contractCode`, so mutations apply directly to the
struct.

Author: weiihann

core/state/stateupdate.go

@@ -83,8 +83,8 @@ type stateUpdate struct {
 	storagesOrigin map[common.Address]map[common.Hash][]byte
 	rawStorageKey  bool
 
-	codes map[common.Address]contractCode // codes contains the set of dirty codes
-	nodes *trienode.MergedNodeSet         // Aggregated dirty nodes caused by state changes
+	codes map[common.Address]*contractCode // codes contains the set of dirty codes
+	nodes *trienode.MergedNodeSet          // Aggregated dirty nodes caused by state changes
 }
 
 // empty returns a flag indicating the state transition is empty or not.
@@ -104,7 +104,7 @@ func newStateUpdate(rawStorageKey bool, originRoot common.Hash, root common.Hash
 		accountsOrigin = make(map[common.Address][]byte)
 		storages       = make(map[common.Hash]map[common.Hash][]byte)
 		storagesOrigin = make(map[common.Address]map[common.Hash][]byte)
-		codes          = make(map[common.Address]contractCode)
+		codes          = make(map[common.Address]*contractCode)
 	)
 	// Since some accounts might be destroyed and recreated within the same
 	// block, deletions must be aggregated first.
@@ -126,7 +126,7 @@ func newStateUpdate(rawStorageKey bool, originRoot common.Hash, root common.Hash
 		// Aggregate dirty contract codes if they are available.
 		addr := op.address
 		if op.code != nil {
-			codes[addr] = *op.code
+			codes[addr] = op.code
 		}
 		accounts[addrHash] = op.data