Merge pull request ibmruntimes#866 from JasonFengJ9/previewfeatures

Temporarily restore PreviewFeature.Feature.FOREIGN & STRING_TEMPLATES

Author: pshipton

src/java.base/share/classes/jdk/internal/javac/PreviewFeature.java

@@ -89,6 +89,9 @@ public enum Feature {
         // Not used, but required by interim javac with Java 21 bootjdk.
         @JEP(number=445, title="Unnamed Classes and Instance Main Methods", status="Deprecated")
         UNNAMED_CLASSES,
+        FOREIGN,
+        @JEP(number=459, title="String Templates", status="Second Preview")
+        STRING_TEMPLATES,
         /**
          * A key for testing.
          */