Add issue resource_iteration_events to Project Import/Export

- Add resource_iteration_events to issues when using Project
  Import/Export in order to associated issues with iterations
- Having issues associated with iterations allows to show
  burn up/down charts on iteration pages correctly

Changelog: added
EE: true

doc/user/group/import/index.md

@@ -92,6 +92,7 @@ migrated:
 - Finisher
 - Group Labels ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/292429) in 13.9)
 - Iterations ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/292428) in 13.10)
+- Iterations cadences ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/96570) in 15.4)
 - Members ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/299415) in 13.9)
   Group members are associated with the imported group if:
   - The user already exists in the target GitLab instance and
@@ -117,8 +118,10 @@ On self-managed GitLab, migrating project resources are not available by default
   - CI Pipelines ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/339407) in GitLab 14.6)
   - Designs ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/339421) in GitLab 15.1)
   - Issues ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/267946) in GitLab 14.4)
+    - Issue iteration ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/96184) in 15.4)
     - Issue resource state events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
     - Issue resource milestone events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
+    - Issue resource iteration events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
   - Labels ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/339419) in GitLab 14.4)
   - LFS Objects ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/339405) in GitLab 14.8)
   - Members ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/341886) in GitLab 14.8)

doc/user/group/settings/import_export.md

@@ -60,6 +60,7 @@ The following items are exported:
 - Events
 - [Wikis](../../project/wiki/group.md)
   ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53247) in GitLab 13.9)
+- Iterations cadences ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/95372) in 15.4)
 
 The following items are **not** exported:
 

doc/user/project/settings/import_export.md

@@ -72,8 +72,10 @@ Items that are exported include:
 - Project configuration, excluding integrations
 - Issues
   - Issue comments
+  - Issue iteration ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/96184) in 15.4)
   - Issue resource state events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
   - Issue resource milestone events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
+  - Issue resource iteration events ([Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/291983) in GitLab 15.4)
 - Merge requests
   - Merge request diffs
   - Merge request comments