Add READ_MEDIA_VISUAL_USER_SELECTED to apps automatically

If an app requests READ_MEDIA_VIDEO/IMAGES, we should add
READ_MEDIA_VISUAL_USER_SELECTED automatically.

Also updates documentation

Bug: 256921561
Bug: 251783841
Test: atest PhotoPickerPermissionTest
Change-Id: I2ddb2caeeacd8c1d65b7892ea7fc22c024f69325