Split MOUNT_FLAG_VISIBLE into MOUNT_FLAG_VISIBLE_FOR_{READ, WRITE}

IVold.MOUNT_FLAG_VISIBLE is split into MOUNT_FLAG_VISIBLE_FOR_READ and
MOUNT_FLAG_VISIBLE_FOR_WRITE.
Accordingly, VolumeBase::MountFlags::kVisible is split into
kVisibleForRead and kVisibleForWrite.

Bug: 206019156
Test: m
Change-Id: Ia55673400d9f713f221650e1335a46ba11f6f027
Merged-In: Ia55673400d9f713f221650e1335a46ba11f6f027
5 files changed