Configure functional gating

- Tier 0 is defined by `plans/tier0.fmf`. The pipelines take care of
  running it. The results are presented as "osci.tier0".

- Tier 1 is configured in, triggered and executed by BaseOS CI. The
  respective jobs there are called:

    baseos-ci.brew-build.gate-build-fast-lane.functional
    baseos-ci.brew-build.gate-build-slow-lane.functional

  Here in `gating.yaml`, we just tell GitLab OSCI that is must wait
  for these jobs and they must pass for successful gating. The results
  are presented under the same names as the jobs have.

.fmf/version

@@ -0,0 +1 @@
+1

gating.yaml

@@ -1,6 +1,7 @@
 --- !Policy
 product_versions:
-  - rhel-8
+  - rhel-9
 decision_context: osci_compose_gate
 rules:
-  - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.tier1.functional}
+  - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.gate-build-fast-lane.functional}
+  - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.gate-build-slow-lane.functional}

plans/tier0.fmf

@@ -0,0 +1,34 @@
+# Tier 0 test plan. It's actually Tier 1
+#   - limited to its public part
+#   - executed on the architecture at hand
+# When run by osci.tier0 on CentOS Stream or RHEL, it receives the following
+# context:
+#   arch=x86_64 (the architecture at hand, currently OSCI uses just x86_64)
+#   distro=rhel<M>.<m> (even for CentOS Stream builds)
+#   trigger=build
+
+summary: Tier 0 test plan
+context:
+  component: compat-sap-c++-13
+discover:
+  - name: collect_info
+    how: shell
+    tests:
+      - name: /info/rpms
+        test: rpm -qa --last
+  - name: public_tests
+    how: fmf
+    url: https://gitlab.com/redhat/centos-stream/tests/compat-sap-cplusplus.git
+    filter: tier:1
+prepare+:
+  - how: shell
+    script:
+      - dnf config-manager --set-enabled '*CRB*' || true
+      - dnf config-manager --set-enabled '*CodeReady*' || true
+      - dnf config-manager --set-enabled '*crb*' || true
+      - dnf config-manager --set-enabled '*[Bb]uildroot*' || true
+      - dnf config-manager --set-enabled '*SAP*' || true
+execute:
+  how: tmt
+environment+:
+  PACKAGE: compat-sap-c++-13