Rather than implementing V2-library and static-library-reference support
in a new block, we will be enhancing the existing `LibraryContentBlock`
in-place.

Relevant ADR PR: #33231

Co-Authored-By: Connor Haugh <chaugh@2u.com>
Co-Authored-By: Eugene Dyudyunov <evgen.dyudyunov@raccoongang.com>

…m into kdmccormick/library-content-v2

...per comment in cms/djangoapps/contentstore/tasks.py.

This fixes an exception that was raised in the background whenever
the update_children_task was started:

     Traceback (most recent call last):
       File "/openedx/venv/lib/python3.8/site-packages/celery/utils/dispatch/signal.py", line 276, in send
         response = receiver(signal=self, sender=sender, **named)
       File "/openedx/venv/lib/python3.8/site-packages/user_tasks/signals.py", line 215, in start_user_task
         sender.status.start()
       File "/openedx/venv/lib/python3.8/site-packages/user_tasks/tasks.py", line 84, in status
         name = self.generate_name(arguments_dict)
       File "/openedx/edx-platform/openedx/core/djangoapps/content_libraries/tasks.py", line 274, in generate_name
         key = arguments_dict['dest_block_key']
     KeyError: 'dest_block_key'

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Just like ./common/ and ./openedx/, the unit tests in ./xmodule/
validate behavior in both LMS and CMS. In order to fully test
./xmodule/, we need to run its tests in both contexts.

Also in this commit:

* refactor: Rename the shards to be clear whether they're
            running under LMS or CMS.
* docs: correct comments regarding conditions under which
        codejail's test_cant_do_something_forbidden is skipped.

* test: update a unit test which was using the now-deleted
        library_sourced block to use library_content block instead.

This reverts commit f1370d0.

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This reverts commit 535fb52.

This reverts commit 0cf735f.

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…etter debugging

…ust syncing

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"refreshing" was ambiguous, possibly meaning either:

a. syncing the lc block's children with the library, or
b. reselecting the particular set of lc block children that learner
sees.

…thod

the handler checks permissions, the internal method doesn't.

this is necessary to fix tests. it also makes the internal method
consistent with sync_from_library, which doesn't check perms either.

…flag

…ssary

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… changes

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