Enable gating through fmf plans in TMT.

For now both an old way and new way through fmf plans is enabled. The
legacy way to be disabled once the fmf plans are verified to work.

.fmf/version

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

ci.fmf

@@ -0,0 +1 @@
+resultsdb-testcase: separate

gating.yaml

@@ -5,3 +5,4 @@ decision_context: osci_compose_gate
 rules:
   - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.tier1-gating.functional}
   - !PassingTestCaseRule {test_case_name: baseos-ci.brew-build.ci-dnf-stack-gating.functional}
+  - !PassingTestCaseRule {test_case_name: osci.brew-build./plans/internal/CI-Tier-1.functional}

plans/internal/CI-Tier-1.fmf

@@ -0,0 +1,23 @@
+summary: Internal CI-Tier-1 tests plan
+discover:
+  - name: dnf
+    how: fmf
+    filter: 'tag: CI-Tier-1'
+    url: https://pkgs.devel.redhat.com/git/tests/dnf
+  - name: libdnf
+    how: fmf
+    filter: 'tag: CI-Tier-1'
+    url: https://pkgs.devel.redhat.com/git/tests/libdnf
+  - name: libmodulemd
+    how: fmf
+    filter: 'tag: CI-Tier-1'
+    url: https://pkgs.devel.redhat.com/git/tests/libmodulemd
+  - name: yum
+    how: fmf
+    filter: 'tag: CI-Tier-1'
+    url: https://pkgs.devel.redhat.com/git/tests/yum
+execute:
+    how: tmt
+adjust:
+    enabled: false
+    when: distro == centos-stream or distro == fedora