Add Stopwatch::resume method

Marlin/src/libs/stopwatch.cpp

   else return false;
 }
 
+void Stopwatch::resume(const millis_t duration) {
+  #if ENABLED(DEBUG_STOPWATCH)
+    Stopwatch::debug(PSTR("resume"));
+  #endif
+
+  reset();
+  if ((accumulator = duration)) state = RUNNING;
+}
+
 void Stopwatch::reset() {
   #if ENABLED(DEBUG_STOPWATCH)
     Stopwatch::debug(PSTR("reset"));
   accumulator = 0;
 }
 
-bool Stopwatch::isRunning() {
-  return (state == RUNNING) ? true : false;
-}
-
-bool Stopwatch::isPaused() {
-  return (state == PAUSED) ? true : false;
-}
-
 millis_t Stopwatch::duration() {
-  return (((isRunning()) ? millis() : stopTimestamp)
+  return ((isRunning() ? millis() : stopTimestamp)
           - startTimestamp) / 1000UL + accumulator;
 }
 

Marlin/src/libs/stopwatch.h

     FORCE_INLINE static void init() { reset(); }
 
     /**
-     * @brief Stops the stopwatch
-     * @details Stops the running timer, it will silently ignore the request if
-     * no timer is currently running.
-     * @return true is method was successful
+     * @brief Stop the stopwatch
+     * @details Stop the running timer, it will silently ignore the request if
+     *          no timer is currently running.
+     * @return true on success
      */
     static bool stop();
 
     /**
      * @brief Pause the stopwatch
      * @details Pause the running timer, it will silently ignore the request if
-     * no timer is currently running.
-     * @return true is method was successful
+     *          no timer is currently running.
+     * @return true on success
      */
     static bool pause();
 
     /**
      * @brief Start the stopwatch
      * @details Start the timer, it will silently ignore the request if the
-     * timer is already running.
-     * @return true is method was successful
+     *          timer is already running.
+     * @return true on success
      */
     static bool start();
 
     /**
+     * @brief Resume the stopwatch
+     * @details Resume a timer from a given duration
+     */
+    static void resume(const millis_t duration);
+
+    /**
      * @brief Reset the stopwatch
      * @details Reset all settings to their default values.
      */
      * @details Return true if the timer is currently running, false otherwise.
      * @return true if stopwatch is running
      */
-    static bool isRunning();
+    FORCE_INLINE static bool isRunning() { return state == RUNNING; }
 
     /**
      * @brief Check if the timer is paused
      * @details Return true if the timer is currently paused, false otherwise.
      * @return true if stopwatch is paused
      */
-    static bool isPaused();
+    FORCE_INLINE static bool isPaused() { return state == PAUSED; }
 
     /**
      * @brief Get the running time