Blog updates and enhancements 2025

[chalin]

• [x] Rendering support for blog-section content:
  • [x] #5885 - custom change
  • [x] https://github.com/google/docsy/pull/2157 - upstreamed
  • [x] Update Docsy - #5915
• [x] Drop .td-breadcrumbs__single style override once Docsy updated with https://github.com/google/docsy/pull/2160, which will affect the blog-index page - #5915
• [x] Drop override that displays the blog-post-is-dated notice once Docsy supports this feature - #5915
• [x] Drop layouts/blog/baseof.html override once the following lands: https://github.com/google/docsy/pull/2161 - #5915
• [x] #5873
• [ ] #6329
• [ ] ...