Docs: Refactor Auto DevOps

What does this MR do?

• CTRT
• Improve readability (12.26 => 10.80)
• Organize topics by workflow
• Simplify content
• Remove redundancies
• Requirement sections moved to requirements.md.
• Addresses #327171 (closed)

Review apps:

Page	What has changed	URL
Auto DevOps index	Refactored	http://main-ee-65772.178.62.207.141.nip.io/ee/topics/autodevops/index.html
Auto DevOps requirements	Content now includes base domain and deployment strategy	http://main-ee-65772.178.62.207.141.nip.io/ee/topics/autodevops/requirements.html
Multiple clusters	Content moved from index to a new page	http://main-ee-65772.178.62.207.141.nip.io/ee/topics/autodevops/multiple_clusters_auto_devops.html

Before/After:

BEFORE	AFTER

Update:

It looks like I didn't understand the issue technical-writing#395 (comment 613502900) very well so I'm shipping !66153 (merged) to address it. This MR refactors the Auto DevOps page instead. I'll drop the priority labels here so we don't have unnecessary pressure to finish it.

Author's checklist

• Follow the Documentation Guidelines and Style Guide.
• Ensure that the product tier badge is added to doc's h1.
• Request a review based on the documentation page's metadata and associated Technical Writer.

To dos:

• Self review
• Fix linter issues:
  • Docs linters
  • App/views (app/views/clusters/clusters/_multiple_clusters_message.html.haml) I'll push this later so that we don't have to run the entire pipeline at every push.
• Request review

Review checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.