refactor: organise TypeScript config and migrate helpers (#44747)

* feat: allow more 1000 steps to be created at once

* refactor: start migrating to typescript

* refactor: delete-step to ts

* refactor: migrated some helpers

* refactor: migrate create-empty-steps

* refactor: migrate create-step-between

* refactor: finish migrating to TS

* refactor: migrate tests

* fix: ensure mock.restore is done after each test

* fix: prevent double-tscing

* fix: repair the tests

* chore: use ts-node for scripts

We don't need the performance boost of incremental compilation and
ts-node is easier to work with

* refactor: consolidate tsconfigs

* refactor: replace gulp

* fix: use ts-node for build-curriculum

* fix: allow ts compilation of config

* feat: create and use create:config script

* fix: add /config to eslint projects

* fix: remove gulp script

tools/challenge-helper-scripts/helpers/pad-with-leading-zeros.test.js

@@ -13,20 +13,6 @@ describe('padWithLeadingZeros helper', () => {
     expect(padWithLeadingZeros('111')).toEqual('111');
   });
 
-  it('should throw on invalid values', () => {
-    const items = ['undefined', null, []];
-
-    items.forEach(item =>
-      expect(() => {
-        if (item !== 'undefined') {
-          padWithLeadingZeros(item);
-        } else {
-          padWithLeadingZeros();
-        }
-      }).toThrow()
-    );
-  });
-
   it('should throw on valid values that are longer that 3 characters', () => {
     expect(() => {
       padWithLeadingZeros('19850809');