[WIP]: Created a sub-dir for agent with a proposed TOC

[Amrita42]

Scope/Objective Create a table of content for the Agent-based Installation book which is part of the Installing book. You can see the placeholder for Agent-based Installation content in the preview below. We need the first PR to be merged into docs.openshift and then we can build on that.

• Applies to main and 4.12
• Currently addresses the following jiras:
• Agent-9
• Agent-248
• Agent-6

Preview NOTE : Requires VPN. The preview is updated as of 18th October.

Update history

• Removed best practices section, we can cover this in the next PR.
• 20/Sept: Removed Agent 5 as part of the scope. agent-5 is interrelated to agent-11. Will cover in the next PR.
• 26/Sept: Removed Troubleshooting section (created a separate OSDOCS jira to track that. Added the workflow diagram -4th Oct: Added Validations content -11th Oct Re-structured TOC and add sample ZTP files , install-config file -14th Oct -implemented SME feedback -18th Oct-Implemented SME feedback

[ocpdocs-previewbot]

🤖 Updated build preview is available at: https://48673--docspreview.netlify.app

Build log: https://circleci.com/gh/ocpdocs-previewbot/openshift-docs/2703

[Amrita42]

@celebdor @zaneb @pawanpinjarkar @bfournie @mhanss please use the preview link, it shows the latest changes. This PR addresses agent-9/248/6 as the scope and is the first Agent-based Installer content. Also please review the call-outs for the sample install-config and the ZTP manifests. Thanks.

[celebdor]

/lgtm

[Amrita42]

@mhanss please review or add lgtm label if all looks good.

[Amrita42]

/label peer-review-needed

[Amrita42]

Note : QE ack pending

[Amrita42]

/label peer-review-needed

[stevsmit]

@Amrita42 great job. PM me if you have questions/concerns!

[Amrita42]

@mhanss I need a QE ack on a priority basis. ptal

[mhanss]

/lgtm

[Amrita42]

/label merge-review-needed

[mburke5678]

/cherrypick enterprise-4.12

[openshift-cherrypick-robot]

@mburke5678: new pull request created: #52444

In response to this:

/cherrypick enterprise-4.12

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