feat: remove legacy library content block from component templates

[salman2013]

Summary

• Removes the library template from the Studio add-component strip, preventing creation of new LegacyLibraryContentBlock instances via the UI
• Removes 'library' from COMPONENT_TYPES, its display name entry, the library block types loop, the component_not_supported_by_library list, and the libraries_v1_enabled() filter in _filter_disabled_blocks

Existing library_content blocks are fully unaffected:

• Randomized settings editor continues to work
• "View all" still navigates to the MFE-based children view
• Migration to v2 libraries still works

Companion frontend PR: openedx/frontend-app-authoring#3180

Ticket: #38058

Test plan

• Verify the "Legacy Library Content" button no longer appears in the add-component strip on a course unit
• Verify existing library_content blocks still render correctly
• Verify the randomized settings editor still works on existing legacy library content blocks
• Verify "View all" still navigates to the MFE-based children view
• Verify migration of legacy library content blocks to v2 still works

Testing Results

[openedx-webhooks]

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[kdmccormick]

The approach looks good! Can you also confirm that the legacy library block doesn't show up under "Advanced" ?

Please have someone else from Aximprovements review as well @salman2013 and then I'll approve and merge.

[salman2013]

The advanced component is not showing the legacy library component.

[farhan]

I have tested the PR manually, PR looks good to me.

I got confused while ready docs from https://docs.openedx.org/en/latest/educators/how-tos/course_development/exercise_tools/use_randomized_content_blocks.html#add-a-randomized-content-block-to-your-course

Select Advanced, and then select Randomized Content Block. The randomized content block is added to your unit.

This line needs to be updated, make sure we have followup story to update the docs

[kdmccormick]

good call out @farhan . we have a story here: openedx/docs.openedx.org#1396 . I added the docs you found to it.

[kdmccormick]

Thanks @salman2013 !

I added an exclamation point to the commit type (feat!:) and added a BREAKING CHANGE note to the commit: d29e27c. Please make sure to do that going forward as it will help our release notes auto-generate with the right breaking change notices.