Improved Issues experience on Work Items framework
## Why
- See https://gitlab.com/groups/gitlab-org/-/epics/6033#problem
## Pre-requisites
- The child and blocking issues/epics need to be resolved before we can migrate issues to work items.
- [Migration critical path](https://docs.google.com/spreadsheets/d/1D3QZ5L2hb7yzIyYnob13o3Mk2vxzCplR-hc5GFmr38c/edit#gid=0)
## Proposal
- Migrate issues to the work item architecture.
- The work item of type `Issue` has parity with the legacy issue use cases.
## Progress
- https://gitlab.com/gitlab-org/gitlab/-/issues/458986
epic