The partitioning code was very outdated, and required a full refactor.
The new subsystem removes duplicated code and uses more AK containers.
The most important change is that all implementations of the
PartitionTable class conform to one interface, which made it possible
to remove unnecessary code in the EBRPartitionTable class.
Finding partitions is now done in the StorageManagement singleton,
instead of doing so in init.cpp.
Also, now we don't try to find partitions on demand - the kernel will
try to detect if a StorageDevice is partitioned, and if so, will check
what is the partition table, which could be MBR, GUID or EBR.
Then, it will create DiskPartitionMetadata object for each partition
that is available in the partition table. This object will be used
by the partition enumeration code to create a DiskPartition with the
correct minor number.
