Set up Netlify build config to ensure previews are not tagged as production, etc

[chalin]

Current config uses Netlify-generated defaults: https://app.netlify.com/sites/cncf-techdocs/configuration/deploys#build-settings.

• Analytics docs rework: factor out UA-to-GA4 instructions, and more #312
• Remove config options from Netlify, since these will be overridden by the netlify.toml file of Analytics docs rework: factor out UA-to-GA4 instructions, and more #312