Add missing Widget of the Week videos to widget API docs

[piedcipher]

Add missing Widget of the Week videos to widget API docs.

Audited all 181 videos and added missing ones in the docs.

Fixes #191031

Also check flutter/packages#12468

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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[github-actions]

This pull request contains changes to Material or Cupertino, which are currently frozen in this repository.

Changes should be made in material_ui and/or cupertino_ui in the flutter/packages repository.

Please refer to #188444 for instructions.

[gemini-code-assist]

Code Review

This pull request adds YouTube video links to the documentation of various Flutter widgets, including CupertinoSliverNavigationBar, CarouselView, SearchAnchor, SearchBar, SegmentedButton, SliverToBoxAdapter, SliverSemantics, Expansible, Magnifier, NestedScrollView, OverlayPortal, and SliverFillRemaining. It also includes a minor formatting improvement to the RawImage class. A review comment identifies that the YouTube link added to the Expansible widget documentation is incorrect and should be updated to point to the appropriate resource.

[Piinks]

The changes in widgets/ can stay here. For cupertino and material, they can head on over to material_ui and cupertino_ui in flutter/packages.

[jmagman]

Thanks for your contribution!
Per #191070 (comment) the changes to packages/flutter/lib/src/cupertino and packages/flutter/lib/src/material will instead need to be made in https://github.com/flutter/packages for cupertino_ui and material_ui. Could you revert the changes and we'll review the just the widgets additions?

[piedcipher]

thanks for the review!

done

[piedcipher]

The changes in widgets/ can stay here. For cupertino and material, they can head on over to material_ui and cupertino_ui in flutter/packages.

thanks for the review!

done

[Piinks]

LGTM