[UDFS] Move large mount-time bitmap/VAT buffers to PagedPool

[Copilot]

UDFS mount on low-memory systems still consumed large NonPagedPool buffers in bitmap/VAT paths, preventing the intended benefit of pagefile-backed memory and blocking large-volume mount scenarios. This change shifts those large mount-time allocations to pageable pool so they can be backed by the system page file.

• Mount-path bitmap buffers made pageable

  • UDFPrepareXSpaceBitmap: _XSBM allocation switched to PagedPool
  • UDFAddXSpaceBitmap / UDFVerifyXSpaceBitmap: temporary bitmap read buffers switched to PagedPool
  • UDFBuildFreeSpaceBitmap: FSBM_Bitmap and FSBM_Bitmap_owners switched to PagedPool
  • UDFGetDiskInfoAndVerify: FSBM_OldBitmap switched to PagedPool

• VAT table buffer made pageable

  • UDFLoadVAT: Vcb->Vat allocation switched to PagedPool

• Scope

  • Only pool type selection was changed for the targeted large allocations; allocation sizes, control flow, and bitmap/VAT logic are unchanged.

// before
Vcb->Vat = (uint32*)DbgAllocatePool(NonPagedPool, (Vcb->LastPossibleLBA+1)*sizeof(uint32));

// after
Vcb->Vat = (uint32*)DbgAllocatePool(PagedPool, (Vcb->LastPossibleLBA+1)*sizeof(uint32));