[wallet] Move getBlockHash from Chain::Lock interface to simple Chain

src/interfaces/chain.h

@@ -87,9 +87,6 @@ public:
     public:
         virtual ~Lock() {}
 
-        //! Get block hash. Height must be valid or this function will abort.
-        virtual uint256 getBlockHash(int height) = 0;
-
         //! Check that the block is available on disk (i.e. has not been
         //! pruned), and contains transactions.
         virtual bool haveBlockOnDisk(int height) = 0;
@@ -135,6 +132,9 @@ public:
     //! included in the current chain.
     virtual Optional<int> getBlockHeight(const uint256& hash) = 0;
 
+    //! Get block hash. Height must be valid or this function will abort.
+    virtual uint256 getBlockHash(int height) = 0;
+
     //! Return whether node has the block and optionally return block metadata
     //! or contents.
     virtual bool findBlock(const uint256& hash, const FoundBlock& block={}) = 0;