[caffe2][be] migrate gloabl static initializer (pytorch#128784)

Summary:
Caffe2 lib has 200+ global static initializer usage, which are papar-cut reference to startup perf. Detail in this post https://fb.workplace.com/groups/arglassesperf/permalink/623909116287154.

This Diff migrate StorageImpl.cpp

Addtional Context: https://fb.workplace.com/groups/arglassesperf/permalink/623909116287154

Test Plan: CI

Differential Revision: D58639283

Pull Request resolved: pytorch#128784
Approved by: https://github.com/aaronenyeshi

c10/core/StorageImpl.cpp

@@ -7,9 +7,12 @@ namespace c10 {
 C10_API std::array<StorageImplCreateHelper, at::COMPILE_TIME_MAX_DEVICE_TYPES>
     StorageImplCreate;
 
-// A allowlist of device type, currently available is PrivateUse1.
-static ska::flat_hash_set<c10::DeviceType> DeviceTypeAllowList{
-    DeviceType::PrivateUse1};
+// A allowlist of device type, currently available is PrivateUse1
+inline ska::flat_hash_set<c10::DeviceType>& GetBackendMetaAllowlist() {
+  static ska::flat_hash_set<c10::DeviceType> DeviceTypeAllowList{
+      DeviceType::PrivateUse1};
+  return DeviceTypeAllowList;
+}
 
 void throwNullDataPtrError() {
   TORCH_CHECK(
@@ -41,8 +44,9 @@ void SetStorageImplCreate(DeviceType t, StorageImplCreateHelper fptr) {
   // Allowlist verification.
   // Only if the devicetype is in the allowlist,
   // we allow the extension to be registered for storageImpl create.
+  const auto& DeviceTypeAllowlist = GetBackendMetaAllowlist();
   TORCH_CHECK(
-      DeviceTypeAllowList.find(t) != DeviceTypeAllowList.end(),
+      DeviceTypeAllowlist.find(t) != DeviceTypeAllowlist.end(),
       "It is only allowed to register the storageImpl create method ",
       "for PrivateUse1. ",
       "If you have related storageImpl requirements, ",