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

tsconfig-base.json

@@ -0,0 +1,26 @@
+{
+  "compilerOptions": {
+    "lib": ["WebWorker", "DOM", "DOM.Iterable"],
+    "target": "es2020",
+    "module": "es2020",
+    "moduleResolution": "node",
+    "allowJs": true,
+    "jsx": "react",
+    "strict": true,
+    "esModuleInterop": true,
+    "experimentalDecorators": true,
+    "emitDecoratorMetadata": true,
+    "noEmit": true,
+    "resolveJsonModule": true,
+    "skipLibCheck": true,
+    "types": ["node", "jest", "@testing-library/jest-dom"]
+  },
+  // since ts-node compiles ts on the fly and then uses node, it needs to
+  // compile the scripts to commonjs (or node will complain about the requires)
+  "ts-node": {
+    "compilerOptions": {
+      "module": "commonjs"
+    },
+    "transpileOnly": true
+  }
+}