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).
maybeStrictRoot = fiber;
      }
      fiber = fiber.return;
    }
    return maybeStrictRoot;
  };
  ReactStrictModeWarnings.recordLifecycleWarnings = (
    fiber: Fiber,
    instance: any,
  ) => {
    const strictRoot = getStrictRoot(fiber);
    
    
    
    
    
    if (didWarnSet.has(fiber.type)) {
      return;
    }
    let warningsForRoot;
    if (!pendingWarningsMap.has(strictRoot)) {
      warningsForRoot = {
        UNSAFE_componentWillMount: [],
        UNSAFE_componentWillReceiveProps: [],
        UNSAFE_componentWillUpdate: [],
      };
      pendingWarningsMap.set(strictRoot, warningsForRoot);
    } else {
      warningsForRoot = pendingWarningsMap.get(strictRoot);
    }