Split access-media-storage from read-external-storage

And also pre-grant it to all apps that currently get any storage
permission pre-granted

cherry-pick for qt-qpr1-dev Ib9f50d25c002036f13cf2d42fc4d1b214f20920c

Test: - straight cherry-pick
      - atest SplitPermissionTest
Bug: 141048840,140961754
Change-Id: Ia2219639a2104965a382ffef647e5ebaa0f9d540