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

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