Add a simple python script to generate a new test (#3972)

The current default citus settings for tests are not really best
practice anymore. However, we keep them because lots of tests depend on
them.

I noticed that I created the same test harness for new tests I added all
the time. This is a simple script that generates that harness, given a
name for the test.

To run:

src/test/regress/bin/create_test.py my_awesome_test

src/test/regress/bin/create_test.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+
+import sys
+import random
+import os
+
+if len(sys.argv) != 2:
+    print(
+        "ERROR: Expected the name of the new test as an argument, such as:\n"
+        "src/test/regress/bin/create_test.py my_awesome_test"
+    )
+    sys.exit(1)
+
+test_name = sys.argv[1]
+
+regress_dir = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
+filename = os.path.join(regress_dir, "sql", f"{test_name}.sql")
+
+if os.path.isfile(filename):
+    print(f"ERROR: test file '{filename}' already exists")
+    sys.exit(1)
+
+shard_id = random.randint(1, 999999) * 100
+
+contents = f"""CREATE SCHEMA {test_name};
+SET search_path TO {test_name};
+SET citus.shard_count TO 4;
+SET citus.shard_replication_factor TO 1;
+SET citus.next_shard_id TO {shard_id};
+
+-- add tests here
+
+SET client_min_messages TO WARNING;
+DROP SCHEMA {test_name} CASCADE;
+"""
+
+
+with open(filename, "w") as f:
+    f.write(contents)
+
+print(f"Created {filename}")
+print(f"Don't forget to add '{test_name}' in multi_schedule somewhere")