BLE: Add API to test the presence of an event handler in a chain.

Author: pan-

connectivity/FEATURE_BLE/include/ble/common/ChainableEventHandler.h

@@ -71,14 +71,14 @@ class ChainableEventHandler
      *
      * @param[in] event_handler Pointer to event handler to remove
      */
-    void removeEventHandler(T* target) {
+    void removeEventHandler(T* event_handler) {
         node_t* to_remove = head;
-        if(head->eh == target) {
+        if(head->eh == event_handler) {
             head = head->next;
         } else {
             auto* it = head;
             while(it->next) {
-                if(it->next->eh == target) {
+                if(it->next->eh == event_handler) {
                     to_remove = it->next;
                     break;
                 }
@@ -94,6 +94,22 @@ class ChainableEventHandler
         delete to_remove;
     }
 
+    /**
+     * Test if an event handler is present in the chain or not.
+     *
+     * @param[in] event_handler Pointer to event handler to check
+     */
+    bool isEventHandlerPresent(T* event_handler) {
+        auto* it = head;
+        while (it) {
+            if (it == event_handler) {
+                return true;
+            }
+            it = it->next;
+        }
+        return false;
+    }
+
 protected:
 
     template<typename... FnArgs, typename... Args>