rpc: Return block time in getblockchaininfo

test/functional/rpc_blockchain.py

@@ -93,11 +93,14 @@ class BlockchainTest(BitcoinTestFramework):
             'pruned',
             'size_on_disk',
             'softforks',
+            'time',
             'verificationprogress',
             'warnings',
         ]
         res = self.nodes[0].getblockchaininfo()
 
+        assert isinstance(res['time'], int)
+
         # result should have these additional pruning keys if manual pruning is enabled
         assert_equal(sorted(res.keys()), sorted(['pruneheight', 'automatic_pruning'] + keys))