Docs IA: Reorganize the "Plan and track work" section for unified work items
As we're introducing more work item types (OKRs, tasks, epics, soon issues), the amount of repeated content in the docs site grows.
This epic tracks work to reorganize the doc set to get closer to single source of truth in these docs.
A common "Work items" view for projects and groups is being added in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/180972+.
Part of https://gitlab.com/gitlab-org/technical-writing/team-tasks/-/issues/1252+
## Docs navigation
I'd like to start laying the foundations to something like this (new or moved is [+green+]):
>>>
- Use GitLab
- Manage your organization
- Organize work with projects
- Plan and track work
- Getting started
- Tutorial: Use GitLab for Scrum +
- Tutorial: Use GitLab for Kanban
- [+Work items+] (new) https://gitlab.com/gitlab-org/gitlab/-/issues/523418
- [+Issues+] +
- [+Tasks+]
- [+Epics+] +
- [+Linked items+] (new) https://gitlab.com/gitlab-org/gitlab/-/issues/510355
- [+Boards +]
- Labels
- Iterations +
- Milestones +
- Comments and threads
- Requirements
- Time tracking
- Customer relations (CRM)
- Wikis +
- Roadmaps
- Objectives and key results (OKR)
- Keyboard shortcuts
- Quick actions +
- Markdown +
- To-Do List
- GitLab Query Language (GLQL)
>>>
epic