Add issue/MR state string to Project Export

changelogs/unreleased/georgekoltsov-fix-issues-mrs-state.yml

+---
+title: Fix issue/MR state not being preserved when importing a project using Project
+  Import/Export
+merge_request: 27816
+author:
+type: fixed

lib/gitlab/import_export/project/import_export.yml

@@ -340,6 +340,7 @@ methods:
     - :diff_head_sha
     - :source_branch_sha
     - :target_branch_sha
+    - :state
   events:
     - :action
   push_event_payload:
@@ -350,6 +351,8 @@ methods:
     - :list_type
   ci_pipelines:
     - :notes
+  issues:
+    - :state
 
 preloads:
   statuses: