[L0] Hook up multi-device compile entry points

Add the `urProgramBuildExp`, `urProgramCompileExp`, and
`urProgramLinkExp` to the loader `ur_program_exp_dditable_t`. Also add
`"ur_exp_multi_device_compile"` to the list of extensions supported by
the L0 adapter, enables the SYCL RT to query support.

Author: kbenzie

source/adapters/level_zero/device.cpp

@@ -190,6 +190,8 @@ UR_APIEXPORT ur_result_t UR_APICALL urDeviceGetInfo(
 
     // Return supported for the UR command-buffer experimental feature
     SupportedExtensions += ("ur_exp_command_buffer ");
+    // Return supported for the UR multi-device compile experimental feature
+    SupportedExtensions += ("ur_exp_multi_device_compile ");
 
     return ReturnValue(SupportedExtensions.c_str());
   }

source/adapters/level_zero/ur_interface_loader.cpp

@@ -440,8 +440,8 @@ UR_DLLEXPORT ur_result_t UR_APICALL urGetProgramExpProcAddrTable(
   if (UR_RESULT_SUCCESS != retVal) {
     return retVal;
   }
-  pDdiTable->pfnBuildExp = nullptr;
-  pDdiTable->pfnCompileExp = nullptr;
-  pDdiTable->pfnLinkExp = nullptr;
+  pDdiTable->pfnBuildExp = urProgramBuildExp;
+  pDdiTable->pfnCompileExp = urProgramCompileExp;
+  pDdiTable->pfnLinkExp = urProgramLinkExp;
   return retVal;
 }