fix(workitems): send status widget when creating a work item

What does this MR do?

CreateWorkItemOptions had no way to set a work item's status, unlike UpdateWorkItemOptions, which already sends it via the status widget. This adds the same Status field to CreateWorkItemOptions and wraps it into the statusWidget of the create mutation input, mirroring the existing update implementation and the pattern used for every other widget.

Confirmed against GitLab's own GraphQL schema (ee/app/graphql/ee/mutations/work_items/create.rb) that WorkItemCreateInput does accept a status_widget argument, matching what's already implemented for update.

Closes #2282 (closed)

Changes

• CreateWorkItemOptions: add Status *WorkItemStatusID
• workItemCreateInputGQL: add StatusWidget *workItemWidgetStatusInputGQL
• CreateWorkItemOptions.wrap(): set StatusWidget when Status is provided
• TestCreateWorkItem_SuccessfulCreationWithAllOptions: extended to assert statusWidget is sent and the resulting work item status is parsed back, using a non-default status (WorkItemStatusInProgress) so the test can't pass by coincidence with the default status

Test plan

• go build ./...
• go vet ./...
• go test ./...