[dataset] use full Timestamp TLV value in otOperationalDataset (#7739)

The `otOperationalDataset#mActiveTimestamp` should represent the full
Active Timestamp TLV value but not only the seconds. The same for
`otOperationalDataset#mPendingTimestamp`.

include/openthread/dataset.h

@@ -213,6 +213,17 @@ typedef struct otOperationalDatasetComponents
     bool mIsChannelMaskPresent : 1;      ///< TRUE if Channel Mask is present, FALSE otherwise.
 } otOperationalDatasetComponents;
 
+/**
+ * This structure represents a Thread Dataset timestamp component.
+ *
+ */
+typedef struct otTimestamp
+{
+    uint64_t mSeconds;
+    uint16_t mTicks;
+    bool     mAuthoritative;
+} otTimestamp;
+
 /**
  * This structure represents an Active or Pending Operational Dataset.
  *
@@ -221,8 +232,8 @@ typedef struct otOperationalDatasetComponents
  */
 typedef struct otOperationalDataset
 {
-    uint64_t                       mActiveTimestamp;  ///< Active Timestamp
-    uint64_t                       mPendingTimestamp; ///< Pending Timestamp
+    otTimestamp                    mActiveTimestamp;  ///< Active Timestamp
+    otTimestamp                    mPendingTimestamp; ///< Pending Timestamp
     otNetworkKey                   mNetworkKey;       ///< Network Key
     otNetworkName                  mNetworkName;      ///< Network Name
     otExtendedPanId                mExtendedPanId;    ///< Extended PAN ID

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (218)
+#define OPENTHREAD_API_VERSION (219)
 
 /**
  * @addtogroup api-instance