[Custom Fields] Interact with custom fields in the work item detail view

Context

• For context about this problem, proposal, implementation roadmap, or UX Research, see &235
• For context about decisions made during the implementation spike, see #472640 (closed)

UX

TBD

Acceptance Criteria

• Reporter+ can view and update custom fields in the work item creation flow
• Updates to custom fields create system notes
• Updates to custom fields are visible in real-time for all connected clients

Note: We may opt for delete instead of archive, but this will be the SSoT for either direction.

Todo

Engineers to create tasks before workflowready for development.

Possible tasks:

• Query supports returning custom fields backend
• Render custom fields widget frontend
• Edit custom fields within the custom fields widget frontend
• Custom field updates are captured in system notes frontend backend
• Mutation supports setting custom field values in the payload backend
• Subscription to update custom field values in real-time backend frontend