fix: fallback to english challenges (#45635)

* fix: fallback to english challenges

All challenges will use the english version if a translated file is not
available.  SHOW_NEW_CURRICULUM still gates what's shown in the client.

* refactor: use closures to simplify createChallenge

* refactor: remove messy destructure

* refactor: add meta via helper

* fix: fallback to [] for meta.required

* fix: repair challenge.block

* refactor: use CONST_CASE for meta + challenge dirs

* fix: catch empty superblocks immediately

* fix: clean up path.resolves

* fix: invalid syntax in JS project steps

* fix: default to english comments and relax tests

Instead of always throwing errors when a comment is not translated, the
tests now warn while SHOW_UPCOMING_CHANGES is true, so that tests will
pass while we're developing and allow translators time to work.

They still throw when SHOW_UPCOMING_CHANGES is false to catch issues
in production

* test: update createCommentMap test

* refactor: delete stale comment

* refactor: clarify validate with explanatory consts

* feat: throw if audited cert falls back to english

* fix: stop testing upcoming localized curriculum

curriculum/schema/challengeSchema.js

@@ -23,7 +23,7 @@ const fileJoi = Joi.object().keys({
 
 const schema = Joi.object()
   .keys({
-    block: Joi.string().regex(slugRE),
+    block: Joi.string().regex(slugRE).required(),
     blockId: Joi.objectId(),
     challengeOrder: Joi.number(),
     removeComments: Joi.bool(),