feat(util): parse section header comments when parsing terraform to adoc

[jacdavi]

🗣 Description

This updates the script for parsing variables.tf into an asciidoc list to find section header comments and include those in the output.
A section header comment starts with ### and captures any text afterwards excluding additional #.

This also updates the m365 adoc which was out of date.

💭 Motivation and context

This alleviates the need to manually add the sections in after running the code.

🧪 Testing

Verified output matched what was being done manually

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• PR targets the correct parent branch (e.g., main or release-name) for merge.
• Changes are limited to a single goal - eschew scope creep!
• Changes are sized such that they do not touch excessive number of files.
• All future TODOs are captured in issues, which are referenced in code comments.
• Related issues these changes resolve are linked preferably via closing keywords.
• All relevant repo and/or project documentation updated to reflect these changes.
• All automated checks (e.g., linting, static analysis, unit/smoke tests) passed.

✅ Post-merge checklist

• Feature branch deleted after merge to clean up repository.
• Verified that all checks pass on parent branch (e.g., main or release-name) after merge.