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