Migrate PrivateAccess from protos to hpb

PiperOrigin-RevId: 670965004

hpb/internal/BUILD

@@ -24,7 +24,9 @@ cc_library(
 cc_library(
     name = "internal",
     hdrs = ["internal.h"],
-    visibility = ["//hpb:__subpackages__"],
+    visibility = [
+        "//hpb:__subpackages__",
+    ],
     deps = [
         "//upb:mem",
         "//upb:message",

protos/protos.h

@@ -10,12 +10,10 @@
 namespace protos {
 namespace internal {
 using hpb::internal::GetInternalMsg;
-using hpb::internal::PrivateAccess;
 using hpb::internal::Serialize;
 using hpb::internal::SetExtension;
 }  // namespace internal
 
-
 using hpb::Arena;
 using hpb::Ptr;
 }  // namespace protos