[CICD] Include steps for 'seco-base' submodule integration

Every time a MR is opened in this repo, the corresponding SHA of the
submodule in the ‘seco-base’ repository must be updated.

.gitlab-ci @ eee2e5d8

+Subproject commit eee2e5d82e58d8ce9d576747f1449c00fc88897f

.gitlab-ci.yml

+---
+# ---------------------------------------------------------------------------------------
+# Include the default CI steps from the gitlab-ci repo
+# ---------------------------------------------------------------------------------------
+include:
+  - project: '${CI_PROJECT_ROOT_NAMESPACE}/infrastructure/gitlab-ci'
+    ref: eee2e5d82e58d8ce9d576747f1449c00fc88897f
+    file: 'tools-integration.yml'
+
+variables:
+  GITLAB_CI_REVISION: eee2e5d82e58d8ce9d576747f1449c00fc88897f
+  SUBMODULE_NAME: seco-layer-manager

.gitmodules

+[submodule ".gitlab-ci"]
+	path = .gitlab-ci
+	url = ../../infrastructure/gitlab-ci