We used to allocate major numbers quite randomly, with no common place
to look them up if needed.
This commit is changing that by placing all major number allocations
under a new C++ namespace, in the API/MajorNumberAllocation.h file.
We also add the foundations of what is needed before we can publish this
information (allocated numbers for block and char devices) to userspace.
It calculated the disk size with the zero-based max addressable block
value.
For example, for a disk device with a block size of 512 bytes that has 2
LBAs so it can address LBA 0 and LBA 1 (so m_max_addressable_block is 1)
the calculated disk size will be 512 instead of 1024 bytes.
We remove can_read() and can_write(), as both of these methods should be
implemented for proper blocking support.
For our case, the previous code will simply block the user if they tries
to read beyond the max addressable offset, which is not a correct
behavior.
Instead, just do proper EOF guarding when calling read() and write() on
such objects.
The Storage subsystem, like the Audio and HID subsystems, exposes Unix
device files (for example, in the /dev directory). To ensure consistency
across the repository, we should make the Storage subsystem to reside in
the Kernel/Devices directory like the two other mentioned subsystems.
