Revamp the `Architecture` page

[vy]

As agreed in the site structure document, revamp the Development page such that

• Improve content, formatting, and sectioning
• Replace images with the ones generated using Antora extensions (This will enable developers to update images by changing a couple of lines of code instead of needing to open images in an editor, keeping separate JPG and XCF files, etc.)
• Target 2.x, port to main