Add support for memory and custom metrics in all HPAs

What does this MR do?

This is a followup of !2555 (merged) for the HorizontalPodAutoscaler update to v2beta2 (#2862 (closed)), adding the following:

• Add support for memory metrics to all HPAs
• Allow specifying either average value or average utilization for cpu/memory metrics in all HPAs
• Add support for custom metrics in all HPAs
• Deprecate hpa.targetAverage{Utilization,Value} in favor of hpa.cpu.targetAverage{Utilization,Value}
• Deprecate hpa.behaviour in favor of hpa.behavior

TODO:

• update the documentation for all charts
• rebase this MR after merging !2555 (merged) and change target branch to master

Related issues

• #2862 (closed)
• https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/15720

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