iOS APP 启动时间优化

附：控制台输出预启动时间log

Total pre-main time: 246.58 milliseconds (100.0%)

         dylib loading time:  72.98 milliseconds (29.5%)

        rebase/binding time:  51.10 milliseconds (20.7%)

            ObjC setup time:  71.53 milliseconds (29.0%)

           initializer time:  50.76 milliseconds (20.5%)

           slowest intializers :

               libSystem.dylib :   2.65 milliseconds (1.0%)

    libMainThreadChecker.dylib :  15.49 milliseconds (6.2%)

                 MediaServices :   8.14 milliseconds (3.3%)

                         ONBUS :  12.92 milliseconds (5.2%)