8224529: [TESTBUG] JFR TestShenandoahHeapRegion* tests fail on build w/o Shenandoah

Fixed at-requires statement, updated TEST.ROOT

Reviewed-by: clanger, egahlin

test/jdk/TEST.ROOT

@@ -43,6 +43,7 @@ requires.properties= \
     sun.arch.data.model \
     java.runtime.name \
     vm.gc.Z \
+    vm.gc.Shenandoah \
     vm.graal.enabled \
     vm.compiler1.enabled \
     vm.compiler2.enabled \

test/jdk/jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionInformationEvent.java

@@ -38,8 +38,7 @@ import jdk.test.lib.jfr.GCHelper;
 /**
  * @test
  * @bug 8221507
- * @requires vm.hasJFR
- * @requires vm.gc == "Shenandoah" | vm.gc == null
+ * @requires vm.hasJFR & vm.gc.Shenandoah
  * @key jfr
  * @library /test/lib /test/jdk
  * @run main/othervm  -Xmx32m -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGarbageThreshold=1 jdk.jfr.event.gc.detailed.TestShenandoahHeapRegionInformationEvent

test/jdk/jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionStateChangeEvent.java

@@ -37,8 +37,7 @@ import jdk.test.lib.jfr.GCHelper;
 /**
  * @test
  * @bug 8221507
- * @requires vm.hasJFR
- * @requires vm.gc == "Shenandoah" | vm.gc == null
+ * @requires vm.hasJFR & vm.gc.Shenandoah
  * @key jfr
  * @library /test/lib /test/jdk
  * @run main/othervm  -Xmx32m -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGarbageThreshold=1 jdk.jfr.event.gc.detailed.TestShenandoahHeapRegionStateChangeEvent