8287597: List all preview features on the javadoc PREVIEW page

Reviewed-by: jjg

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

@@ -59,15 +59,38 @@ public @interface PreviewFeature {
 
     public boolean reflective() default false;
 
+    /**
+     * Enum of preview features in the current release.
+     * Values should be annotated with the feature's {@code JEP}.
+     */
     public enum Feature {
-        SWITCH_PATTERN_MATCHING,
+        @JEP(number=427, title="Pattern Matching for switch", status="Third Preview")
+        SWITCH_PATTERN_MATCHING(),
+        @JEP(number=405, title="Record Patterns")
         RECORD_PATTERNS,
+        @JEP(number=425, title="Virtual Threads")
         VIRTUAL_THREADS,
+        @JEP(number=424, title="Foreign Function & Memory API")
         FOREIGN,
         /**
          * A key for testing.
          */
+        @JEP(number=0, title="Test Feature")
         TEST,
         ;
     }
+
+    /**
+     * Annotation identifying the JEP associated with a preview feature.
+     */
+    @Target(ElementType.FIELD)
+    @Retention(RetentionPolicy.CLASS)
+    @interface JEP {
+        /** JEP number */
+        int number() default 0;
+        /** JEP title in plain text */
+        String title();
+        /** JEP status such as "Preview", "Second Preview", etc */
+        String status() default "Preview";
+    }
 }