Add version 16 support in the rust and python code

test_runner/fixtures/pg_version.py

@@ -17,6 +17,7 @@ This fixture is used to determine which version of Postgres to use for tests.
 class PgVersion(str, enum.Enum):
     V14 = "14"
     V15 = "15"
+    V16 = "16"
     # Instead of making version an optional parameter in methods, we can use this fake entry
     # to explicitly rely on the default server version (could be different from pg_version fixture value)
     NOT_SET = "<-POSTRGRES VERSION IS NOT SET->"