Fairly large reorg of content

What does this MR do?

This MR:

• Moves all of the GitOps and CI/CD topics into their own pages. The GitOps page is new. The CI/CD tunnel page was used to put all the CI/CD info. Will have to rename/redirect this file after merge.
• Moves topics out of the Install page and onto the Configuration/Working with page.
• Uses lowercase for the agent.
• Combines two topics about network security alerts that were similar and marked as deprecated.
• Puts the Scan your container images for vulnerabilities topic on the "Working with" page. This topic can be moved into its own page in a later MR.

If a link was broken on a deprecated page, the link was removed rather than fixed.

The intention with these changes is to make the information easier to find and build on in the future.

The left nav will be updated in relation to these changes:

Before	After
	)

What's not in this MR

This MR does not have a few things that will be handled in follow-up MRs:

• It does not standardize the full docset on lowercase a for agent.
• It does not address pages other than the top-level page, install, configure, and the CI/CD tunnel page.
• It does not ensure the words CI/CD tunnel don't appear elsewhere in the docs. (And doesn't rename/redirect the CI/CD tunnel page.)

Related issues

Related to: technical-writing#528 (closed)

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• Ensure that the product tier badge is added to topic's h1.
• Request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

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 reviews above. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.