8368670: Deadlock in JFR on event register + class load

Reviewed-by: mgronlun

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/internal/MetadataRepository.java

@@ -291,7 +291,7 @@ private byte[] getBinaryRepresentation() {
         }
     }
 
-    synchronized boolean isEnabled(String eventName) {
+    boolean isEnabled(String eventName) {
         return settingsManager.isEnabled(eventName);
     }
 

src/jdk.jfr/share/classes/jdk/jfr/internal/SettingsManager.java

@@ -129,7 +129,7 @@ public void finish() {
         }
     }
 
-   private Map<String, InternalSetting> availableSettings = new LinkedHashMap<>();
+    private volatile Map<String, InternalSetting> availableSettings = new LinkedHashMap<>();
 
     void setSettings(List<Map<String, String>> activeSettings, boolean writeSettingEvents) {
         // store settings so they are available if a new event class is loaded