Test varying upgrade scenarios and test for pain points

Review GitLab upgrade documentation and try various upgrade scenarios to identify and document pain points.

• Review current GitLab upgrade documentation and point out possible pain points.
• Perform Omnibus upgrades and point out pain points.
  • Patch update.
  • Minor version update.
  • Major version update.
• Perform helm chart upgrades and point out pain points.
  • Patch update.
  • Minor version update.
  • Major version update.
• Perform operator upgrades and point out pain points.
  • Patch update.
  • Minor version update.
  • Major version update.
• Multi-node zero-downtime upgrades and point out pain points.
  • Minor version update.
• Multi-node with downtime upgrades and point out pain points.
  • Minor version update.
  • Major version update.