Clean up and restructure the 'semantic_text field type' page

[kosabogi]

The semantic_text field type page has become quite dense over time.

To improve clarity and maintainability, we should break it up into logical subpages and review the content for consistency and readability.

To do:

• Split the page into subpages for better readability
• Look for opportunities to merge interrelated sections for a clearer structure
• Clean up oddly rendered tabs (as shown in the screenshot below), possibly by using different formatting elements such as collapsibles