feat: allow using all components of LibraryContentBlock

[Agrendalath]

Description

Setting max_count to a negative value resulted in raising an unhandled ValueError. With this change, it selects all children of the LibraryContentBlock.

Testing instructions

1. Create a new library in Studio. It should contain at least 2 XBlocks.
2. Add library_content to the Advanced Module List in a course.
3. Create a Randomized Content Block in Studio and set its "Count" to -1.
4. View the XBlock in Studio and check that it has the "Each student will be assigned {x} components drawn randomly from this list. " information ({x} should be the number of available components in the library).
5. Check that all components are displayed in Preview.
6. Publish the course and check that all components are displayed in LMS.

Deadline

"None"

Other information

Private-ref: BB-7062.

[openedx-webhooks]

Thanks for the pull request, @Agrendalath!

As a core committer in this repo, you can merge this once the pull request is approved per the core committer reviewer requirements and according to the agreement with your edX Champion.

[pkulkark]

@Agrendalath LGTM 👍

• I tested this: Verified the RCB shows all the components from library when count is set to -1 as described in testing instructions.
• I read through the code

[openedx-webhooks]

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[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.