Agentless rollback setup and usage

[rosieyohannan]

Description

Adds three new page:

• Set up rollbacks
• Rollback a project using the rollback pipeline
• Rollback by workflow rerun

Also updates to

• Configure deploy markers
• Pipeline values table
• Rearrange deploys section of sidebar to group agentless and release agent setup options

Reasons

A link to a GitHub and/or JIRA issue (if applicable).
Otherwise, a brief sentence about why you made these changes.

Content Checklist

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[sebastian-lerner]

non-blocking comments