[SYCL][Docs] Add sycl_ext_oneapi_virtual_mem extension and implementation

llvm/include/llvm/SYCLLowerIR/DeviceConfigFile.td

@@ -82,6 +82,7 @@ def AspectExt_intel_fpga_task_sequence : Aspect<"ext_intel_fpga_task_sequence">;
 def AspectExt_oneapi_limited_graph : Aspect<"ext_oneapi_limited_graph">;
 def AspectExt_oneapi_private_alloca : Aspect<"ext_oneapi_private_alloca">;
 def AspectExt_oneapi_queue_profiling_tag : Aspect<"ext_oneapi_queue_profiling_tag">;
+def AspectExt_oneapi_virtual_mem : Aspect<"ext_oneapi_virtual_mem">;
 // Deprecated aspects
 def AspectInt64_base_atomics : Aspect<"int64_base_atomics">;
 def AspectInt64_extended_atomics : Aspect<"int64_extended_atomics">;
@@ -139,7 +140,7 @@ def : TargetInfo<"__TestAspectList",
     AspectExt_oneapi_ballot_group, AspectExt_oneapi_fixed_size_group, AspectExt_oneapi_opportunistic_group,
     AspectExt_oneapi_tangle_group, AspectExt_intel_matrix, AspectExt_oneapi_is_composite, AspectExt_oneapi_is_component,
     AspectExt_oneapi_graph, AspectExt_intel_fpga_task_sequence, AspectExt_oneapi_limited_graph,
-    AspectExt_oneapi_private_alloca, AspectExt_oneapi_queue_profiling_tag],
+    AspectExt_oneapi_private_alloca, AspectExt_oneapi_queue_profiling_tag, AspectExt_oneapi_virtual_mem],
     []>;
 // This definition serves the only purpose of testing whether the deprecated aspect list defined in here and in SYCL RT
 // match.