Add four new function specs to exp-inter-process-communication.yml
and update registry.yml to support IPC operations on physical memory
objects:
- urIPCGetPhysMemHandleExp: export an IPC handle for a physical_mem
- urIPCPutPhysMemHandleExp: release the exported IPC handle
- urIPCOpenPhysMemHandleExp: import an IPC handle into a physical_mem
- urIPCClosePhysMemHandleExp: close the imported physical_mem

Also add ENABLE_IPC flag to ur_physical_mem_flags_t in virtual_memory.yml
to allow allocating physical memory that can be shared via IPC handles.

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

Implement urIPCGetPhysMemHandleExp, urIPCPutPhysMemHandleExp,
urIPCOpenPhysMemHandleExp, and urIPCClosePhysMemHandleExp across all
adapters.

Level Zero v2 adapter (full implementation, Linux only):
- physical_mem.hpp: extend ur_physical_mem_handle_t_ with Device, Size,
  EnableIpc fields
- v2/physical_mem.hpp: add ZeIPCPhysMemHandleData struct (pid + DMA-BUF
  fd + size) for cross-process handle exchange via pidfd_getfd(2)
- v2/physical_mem.cpp: chain ze_external_memory_export_desc_t in
  urPhysicalMemCreate when ENABLE_IPC flag is set; extend
  urPhysicalMemGetInfo to return context, device, size and properties;
  implement the four IPC functions using ZeIPCPhysMemHandleData
- device.cpp: report UR_DEVICE_INFO_IPC_PHYSICAL_MEMORY_SUPPORT_EXP
  as true on Linux, false on Windows

Level Zero v1 adapter (unsupported stubs):
- physical_mem.cpp: return UR_RESULT_ERROR_UNSUPPORTED_FEATURE from all
  four IPC functions; urPhysicalMemCreate always passes EnableIpc=false
- device.cpp: report UR_DEVICE_INFO_IPC_PHYSICAL_MEMORY_SUPPORT_EXP
  as false

CUDA, HIP, OpenCL, Native CPU adapters:
- Return UR_RESULT_ERROR_UNSUPPORTED_FEATURE from all four functions
- Register function pointers in ur_interface_loader.cpp
- Report UR_DEVICE_INFO_IPC_PHYSICAL_MEMORY_SUPPORT_EXP as false

Offload adapter:
- Return UR_RESULT_ERROR_UNSUPPORTED_FEATURE from all four functions
- Register function pointers in ur_interface_loader.cpp

Conformance tests:
- Add urIPCGetPhysMemHandleExp.cpp, urIPCPutPhysMemHandleExp.cpp,
  urIPCOpenPhysMemHandleExp.cpp, urIPCClosePhysMemHandleExp.cpp
  with shared fixtures in urIPCPhysMemHandleExpFixtures.hpp
- Update urPhysicalMemCreate.cpp to cover the ENABLE_IPC flag

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

Use std::optional<ze_external_memory_export_desc_t> so the export
descriptor is only created when UR_PHYSICAL_MEM_FLAG_ENABLE_IPC is
set in urPhysicalMemCreate. The optional lives at function scope,
keeping the pointer valid through the zePhysicalMemCreate call.

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

zePhysicalMemGetProperties requires the same context that was used
to create the physical memory object.  Use hPhysMem->Context instead
of the caller-supplied hContext, which may be a different context.
Mark hContext as [[maybe_unused]] since it is now unused on Linux.

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

Replace [[maybe_unused]] ur_context_handle_t hContext with an
unnamed parameter (ur_context_handle_t) in urIPCGetPhysMemHandleExp,
urIPCPutPhysMemHandleExp, and urIPCClosePhysMemHandleExp.

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>