Add GUARDED_BY(cs_wallet) for encrypted_batch, nWalletMaxVersion, m_max_keypool_index and nOrderPosNext

* AddKeyPubKeyWithDB(...) reads encrypted_batch which potentially races with write in the same method.
* IncOrderPosNext(...) reads nOrderPosNext which potentially races with write in BlockDisconnected(...).
* LoadKeyPool(...) reads m_max_keypool_index which potentially races with write in BlockDisconnected(...).
* LoadMinVersion(...) reads nWalletMaxVersion which potentially races with write in BlockDisconnected(...).

src/wallet/wallet.h

@@ -601,13 +601,13 @@ private:
     std::mutex mutexScanning;
     friend class WalletRescanReserver;
 
-    WalletBatch *encrypted_batch = nullptr;
+    WalletBatch *encrypted_batch GUARDED_BY(cs_wallet) = nullptr;
 
     //! the current wallet version: clients below this version are not able to load the wallet
     int nWalletVersion = FEATURE_BASE;
 
     //! the maximum wallet format version: memory-only variable that specifies to what version this wallet may be upgraded
-    int nWalletMaxVersion = FEATURE_BASE;
+    int nWalletMaxVersion GUARDED_BY(cs_wallet) = FEATURE_BASE;
 
     int64_t nNextResend = 0;
     int64_t nLastResend = 0;
@@ -659,7 +659,7 @@ private:
     std::set<int64_t> setInternalKeyPool;
     std::set<int64_t> setExternalKeyPool;
     std::set<int64_t> set_pre_split_keypool;
-    int64_t m_max_keypool_index = 0;
+    int64_t m_max_keypool_index GUARDED_BY(cs_wallet) = 0;
     std::map<CKeyID, int64_t> m_pool_key_to_index;
     std::atomic<uint64_t> m_wallet_flags{0};
 
@@ -754,7 +754,7 @@ public:
     typedef std::multimap<int64_t, CWalletTx*> TxItems;
     TxItems wtxOrdered;
 
-    int64_t nOrderPosNext = 0;
+    int64_t nOrderPosNext GUARDED_BY(cs_wallet) = 0;
     uint64_t nAccountingEntryNumber = 0;
 
     std::map<CTxDestination, CAddressBookData> mapAddressBook;