Add option to show the splashscreen from 'adb shell am'

Add an option to show the splashscreen when launching an appliation :
--splashscreen-show-icon

This will allow to show the splash screen when the application is run
from Android Studio

Bug: 205021357
Test: adb shell am start --splashscreen-show-icon
Change-Id: I09371169bea9c8114c6bf6fe4d486164b5cf561a