Coalesce warnings for deprecated lifecycle hooks and print single message after reconciliation (rather than one per component-type).

Relates to PR #12028 and [this comment](https://github.com/facebook/react/pull/12028#discussion_r162420575).
if (__DEV__) {
      ReactStrictModeWarnings.discardPendingWarnings();
    }
    
    
    
    
    const current = workInProgress.alternate;
    
    startWorkTimer(workInProgress);
    if (__DEV__) {
      ReactDebugCurrentFiber.setCurrentFiber(workInProgress);
    }
    let next = beginFailedWork(
      current,
      workInProgress,
      nextRenderExpirationTime,
    );
    if (__DEV__) {
      ReactDebugCurrentFiber.resetCurrentFiber();
    }
    if (__DEV__ && ReactFiberInstrumentation.debugTool) {
      ReactFiberInstrumentation.debugTool.onBeginWork(workInProgress);
    }
    if (next === null) {
      
      next = completeUnitOfWork(workInProgress);
    }
    ReactCurrentOwner.current = null;