Add support for topologySpreadConstraints

What does this MR do?

Adds support for pod topologySpreadConstraints, this is useful for example to balance number of pods per zone.

Example usage:

gitlab:
  kas:
    topologySpreadConstraints:
      - maxSkew: 1
        topologyKey: zone
        whenUnsatisfiable: ScheduleAnyway
        labelSelector:
          matchLabels:
            app: kas
            release: gitlab

Related issues

• Closes #2890
• Uneven LB traffic gitlab-com/gl-infra/delivery#2296 (moved)
• Nodepool efficiency https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/15901

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened