Update build-gating plan

Collection adjustments no longer needed.
Setup CRB in RHEL to take care of AWS/Beaker repo naming.
Add discover setup for llvm-test-suite

plans/build-gating.fmf

@@ -19,28 +19,14 @@ adjust:
       and trigger != build
     enabled: false
 
-  - because: "When testing SCL-ized LLVM, the collection must be enabled first"
-    environment+:
-      WITH_SCL: "scl enable llvm-toolset-13.0"
-    when: "collection == llvm-toolset-13.0"
-  - because: "When testing SCL-ized LLVM, the collection must be enabled first"
-    environment+:
-      WITH_SCL: "scl enable llvm-toolset-14.0"
-    when: "collection == llvm-toolset-14.0"
-  - because: "When testing SCL-ized LLVM, the collection must be enabled first"
-    environment+:
-      WITH_SCL: "scl enable llvm-toolset-15.0"
-    when: "collection == llvm-toolset-15.0"
-
   # Unfortunately, TMT does not support more declarative approach, we need to run commands on our own.
-  - because: "On RHEL, CRB must be enabled to provide rarer packages"
+  - because: "On RHEL-8+, CRB must be enabled to provide rarer packages"
     prepare+:
       - name: Enable CRB
         how: shell
-        script: dnf config-manager --set-enabled rhel-CRB
+        script: dnf config-manager --set-enabled *-CRB
     when: >-
-      distro == rhel-9
-      or distro == rhel-8
+      distro == rhel and distro >= rhel-8
 
   # Unfortunately, TMT does not support more declarative approach, we need to run commands on our own.
   - because: "On CentOS, CRB must be enabled to provide rarer packages"
@@ -55,6 +41,12 @@ discover:
     - name: clang-tests
       how: fmf
       filter: "tag:-not-in-default"
+    # TODO uncomment when https://src.fedoraproject.org/tests/llvm-test-suite/pull-request/10 is merged
+    # - name: llvm-test-suite
+    #   how: fmf
+    #   url: https://src.fedoraproject.org/tests/llvm-test-suite.git
+    #   ref: main
+    #   test: test-suite
     - name: upstream-llvm-integration-testsuite
       how: fmf
       url: https://src.fedoraproject.org/tests/llvm.git