Upgrade launcher icon and shortcuts to adaptive icon

Bug: 62023774
Test: build, and runs, manual testing on marlin device

Details:
1. Inverted shortcut color and set background to be Grey 100 material color
following the shortcut design guidelines
2. Fixed wrong typecasting in FilesActivity
etc, etc...

Change-Id: I96d245c190ad234aac22fb2e1d58c6e299fb7fcf