test: Test year 2106 block timestamps

* Use maximum timestamp in getblocktemplate test
* Mine block with maximum timestamp and MTP in blockchain test

test/functional/mining_basic.py

@@ -200,7 +200,7 @@ class MiningTest(BitcoinTestFramework):
 
         self.log.info("getblocktemplate: Test bad timestamps")
         bad_block = copy.deepcopy(block)
-        bad_block.nTime = 2**31 - 1
+        bad_block.nTime = 2**32 - 1
         assert_template(node, bad_block, 'time-too-new')
         assert_submitblock(bad_block, 'time-too-new', 'time-too-new')
         bad_block.nTime = 0