Deduplicate kpt function docs

[prachirp]

The kpt function docs had sections which repeated the same content in various ways. This change:

• Refactors all function docs to have all topics have one source of truth page which explains the content in an authoritative way for Deduplicate fn docs #908
• Clarifies examples of running privileged docker containers for Document how to run privileged function docker containers #832
• Fixes W3 Link Checker errors for broken links and reorders links to fit the order they appear on the page
• Adds Next Steps sections to docs which did not have them
• Fixes markdownlint errors in function docs

[frankfarzan]

It's very hard to review changes to 78 files. For future PRs, I suggest splitting this up into manageable chunks and changing one things at a time.