[STORPORT][VIOSTOR] virtio-blk storage path: per-request SCSI contexts, LUN PDOs, and a Storport miniport - #9530

Replace the stub request path with a real implementation:

- PortFdoScsi allocates a per-request STOR_REQUEST_CONTEXT (from a
  look-aside list) plus the miniport's SrbExtension in one allocation,
  publishes it in Srb->SrbExtension, marks the IRP pending before calling
  HwStartIo, and serializes submission with StartIoLock (now actually
  initialized in PortAddDevice).
- StorPortNotification(RequestComplete) finds the context through the
  SrbExtension back-pointer, maps SrbStatus to NTSTATUS, preserves
  IoStatus.Information for SRB_STATUS_DATA_OVERRUN, and queues the
  completion on a 16-byte-aligned SLIST drained by PortCompletionDpc at
  DISPATCH_LEVEL -- no work items, no single-flight gate, so multiple
  requests can be in flight.
- StorPortNotification(IssueDpc) now sets *Succ and forwards the DPC
  arguments; miniport DPCs requested from an ISR are deferred through
  PendingMiniportDpc and queued by the port's interrupt wrapper.
- StorPortGetScatterGatherList builds a per-request SG list from the
  IRP's MDL PFN array; StorPortExtendedFunction gains
  ExtFunctionPutScatterGatherList to free it.
- StorPortGetPhysicalAddress translates addresses inside the SRB data
  buffer through the MDL PFN array instead of calling
  MmGetPhysicalAddress on a process-dependent VA.
- StorPortSynchronizeAccess is implemented via KeSynchronizeExecution.
- PortPdoScsi forwards to PortFdoScsi so SCSI requests sent to a PDO
  reach the miniport.

- PortFdoQueryBusRelations returns a real DEVICE_RELATIONS list built
  from the PDO list under PdoListLock, instead of scanning the bus and
  reporting zero children.
- PortPdoPnp implements START_DEVICE, QUERY_ID (hardware/compatible/
  instance ids built from the inquiry data), QUERY_DEVICE_TEXT,
  TargetDeviceRelation, and REMOVE_DEVICE. BusRelations on a PDO are
  completed without touching IoStatus so partmgr's relations survive.
- PortPdoDeviceControl handles the storage IOCTLs a disk PDO receives
  (STORAGE_QUERY_PROPERTY, IOCTL_DISK_GET_LENGTH_INFO and friends);
  PortDispatchDeviceControl routes PDO requests to it.
- IRP_MN_REMOVE_DEVICE on the FDO drains the request-context look-aside
  list.

New miniport for PCI\VEN_1AF4&DEV_1001 (transitional/legacy virtio-blk):
single split virtqueue, line interrupts, direct descriptors. The request
wire format follows the BSD-3-Clause virtio-win viostor sources; the
Storport integration is ReactOS-specific.

- INQUIRY, READ_CAPACITY(16), MODE_SENSE, TEST_UNIT_READY, VERIFY and
  REQUEST_SENSE are answered locally; READ/WRITE/FLUSH go on the queue.
- Per-request state lives in Srb->SrbExtension; completions are drained
  from the used ring in the ISR and reported via
  StorPortNotification(RequestComplete).
- Negotiates FLUSH, CONFIG_WCE, SEG_MAX and SIZE_MAX; the transfer and
  physical-breaks limits reported to the port come from the negotiated
  device config.
- Debug output through the shared virtio kdebugprint sink defaults to
  off (virtioDebugLevel = 0, bDebugPrint = 0).

The driver answered VPD pages 0x80 and 0x83 with a fixed string
("ROS-VIRTIO-9241-0001"), so every virtio disk reported the same
unique ID. The virtio-blk config space carries no serial field, so
derive a stable serial from the PCI bus/slot and device capacity
instead.

The feature mask dropped VIRTIO_BLK_F_RO, so a read-only virtio disk
was presented as writable and writes failed at the device with a
generic I/O error. Negotiate the feature, fail write CDBs early with
SRB_STATUS_INVALID_REQUEST, and set the WP bit in the MODE_SENSE
device-specific parameter byte.