[netdata] perform SynchronizeServerData() from a Tasklet (#7823)

This commit adds a `Taskelt` in `NetworkData::Notifier` to perform
`SynchronizeServerData()` and post this tasklet when there is a
change and `HandleServerDataUpdated()` is called. This ensures that
if there are multiple changes triggered within the same flow of
execution, they are all synchronized together and included in the
same message to register with leader.

src/core/thread/network_data_notifier.cpp

@@ -46,7 +46,8 @@ namespace NetworkData {
 
 Notifier::Notifier(Instance &aInstance)
     : InstanceLocator(aInstance)
-    , mTimer(aInstance, Notifier::HandleTimer)
+    , mTimer(aInstance, HandleTimer)
+    , mSynchronizeDataTask(aInstance, HandleSynchronizeDataTask)
     , mNextDelay(0)
     , mWaitingForResponse(false)
 {
@@ -55,7 +56,12 @@ Notifier::Notifier(Instance &aInstance)
 void Notifier::HandleServerDataUpdated(void)
 {
     mNextDelay = 0;
-    SynchronizeServerData();
+    mSynchronizeDataTask.Post();
+}
+
+void Notifier::HandleSynchronizeDataTask(Tasklet &aTasklet)
+{
+    aTasklet.Get<Notifier>().SynchronizeServerData();
 }
 
 void Notifier::SynchronizeServerData(void)

src/core/thread/network_data_notifier.hpp

@@ -42,6 +42,7 @@
 #include "common/message.hpp"
 #include "common/non_copyable.hpp"
 #include "common/notifier.hpp"
+#include "common/tasklet.hpp"
 
 namespace ot {
 namespace NetworkData {
@@ -66,6 +67,10 @@ public:
     /**
      * Call this method to inform the notifier that new server data is available.
      *
+     * This method posts a tasklet to sync new server data with leader so if there are multiple changes within the same
+     * flow of execution (multiple calls to this method) they are all synchronized together and included in the same
+     * message to the leader.
+     *
      */
     void HandleServerDataUpdated(void);
 
@@ -85,9 +90,12 @@ private:
                                    Error                aResult);
     void        HandleCoapResponse(Error aResult);
 
+    static void HandleSynchronizeDataTask(Tasklet &aTasklet);
+
     void SynchronizeServerData(void);
 
     TimerMilli mTimer;
+    Tasklet    mSynchronizeDataTask;
     uint32_t   mNextDelay;
     bool       mWaitingForResponse;
 };