Introduce shared responsibility issues and a decentralized triage process

Why is this change being made?

This MR is a step in this issue to iterate on the triage process for issues that lack clear ownership by a group. It introduced the concept of "Share Responsibility Functionality" to the product categories pages. It also provides a clear process for doing triage of these types of issues in a decentralized way that empowers group-level leaders to make decisions.

IMPORTANT: Before reading the changes in this MR and providing feedback, please read first the details in the main issue that this MR is a part of: #14321 (closed)

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added.
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

---