Restructure GADS category pages with social proof content

Removed heading/subheading sections and key_features content from all six category pages. Replaced with hero title 'Automate your infrastructure at any scale / Your Code, Your Cloud, Your Success' and added customer logos, quotes, and community tweets from the /content/b/iac-platform-engineering-idp/ page. Each page maintains category-specific DKI placeholders.

Author: asafashirov