test: create assert_not_equal util and add to where imports are needed

In the functional tests there are lots of cases where we assert != which
this new util will replace, we also are adding the imports and the new assertion

test/functional/wallet_gethdkeys.py

@@ -9,6 +9,7 @@ from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
     assert_raises_rpc_error,
+    assert_not_equal,
 )
 from test_framework.wallet_util import WalletUnlock
 
@@ -59,7 +60,7 @@ class WalletGetHDKeyTest(BitcoinTestFramework):
         # New key is active, should be able to get only that one and its descriptors
         xpub_info = wallet.gethdkeys(active_only=True)
         assert_equal(len(xpub_info), 1)
-        assert xpub_info[0]["xpub"] != xpub
+        assert_not_equal(xpub_info[0]["xpub"], xpub)
         assert "xprv" not in xpub_info[0]
         assert_equal(xpub_info[0]["has_private"], True)
 
@@ -67,7 +68,7 @@ class WalletGetHDKeyTest(BitcoinTestFramework):
         assert_raises_rpc_error(-13, "Error: Please enter the wallet passphrase with walletpassphrase first", wallet.gethdkeys, private=True)
         with WalletUnlock(wallet, "pass"):
             xpub_info = wallet.gethdkeys(active_only=True, private=True)[0]
-            assert xpub_info["xprv"] != xprv
+            assert_not_equal(xpub_info["xprv"], xprv)
             for desc in wallet.listdescriptors(True)["descriptors"]:
                 if desc["active"]:
                     # After encrypting, HD key was rotated and should appear in all active descriptors