Added support for level 3 in widget extensions

What does this MR do and why?

Adds support for level 3 content in the widgets. This data and content is the same as level 2 though it gets indented. These level 3 content areas can be added with the children property in the data.

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #341047 (closed)