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

docs/devops.md

@@ -482,7 +482,7 @@ Provisioning VMs with the Code
 7. Build the server
 
    ```console
-   npm run ensure-env && npm run build:curriculum && npm run build:server
+   npm run create:config && npm run build:curriculum && npm run build:server
    ```
 
 8. Start Instances
@@ -528,7 +528,7 @@ npm ci
 3. Build the server
 
 ```console
-npm run ensure-env && npm run build:curriculum && npm run build:server
+npm run create:config && npm run build:curriculum && npm run build:server
 ```
 
 4. Start Instances

docs/how-to-work-on-localized-client-webapp.md

@@ -19,7 +19,7 @@ Most of files for translating the platform are located in the [`client/i18n`](ht
 
 ```console
   config/i18n
-  └── all-langs.js
+  └── all-langs.ts
   ...
   client/i18n
   ├── configForTests.js
@@ -57,7 +57,7 @@ Most of files for translating the platform are located in the [`client/i18n`](ht
   │       └── trending.json
   ├── locales.test.js
   ├── schema-validation.js
-  └── validate-keys.js
+  └── validate-keys.ts
 ```
 
 Some of these files are translated on our translation platform (Crowdin), some are not.