tests: Check that the last hardened cache upgrade occurs

When loading an older wallet without the last hardened cache, an
automatic upgrade should be performed. Check this in
wallet_backwards_compatibility.py

When migrating a wallet, the migrated wallet should always have the last
hardened cache, so verify in wallet_migration.py

test/functional/test_framework/test_framework.py

@@ -1082,3 +1082,15 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         if self.options.usecli:
             return json.dumps(text)
         return text
+
+    def inspect_sqlite_db(self, path, fn, *args, **kwargs):
+        try:
+            import sqlite3 # type: ignore[import]
+            conn = sqlite3.connect(path)
+            with conn:
+                result = fn(conn, *args, **kwargs)
+            conn.close()
+            return result
+        except ImportError:
+            self.log.warning("sqlite3 module not available, skipping tests that inspect the database")
+