ObjPtr<>-ify ClassLinker::FindClass(), fix 1 stale reference use.

Thread::CreateAnnotatedStackTrace() was using a stale
reference `aste_array_class`.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 31113334
Change-Id: I191907c0053456bb57de425aa6ccd9668df818a2
diff --git a/compiler/optimizing/intrinsics.cc b/compiler/optimizing/intrinsics.cc
index dfe6d79..056f533 100644
--- a/compiler/optimizing/intrinsics.cc
+++ b/compiler/optimizing/intrinsics.cc
@@ -272,7 +272,8 @@
   ClassLinker* class_linker = runtime->GetClassLinker();
   gc::Heap* heap = runtime->GetHeap();
   IntegerValueOfInfo info;
-  info.integer_cache = class_linker->FindSystemClass(self, "Ljava/lang/Integer$IntegerCache;");
+  info.integer_cache =
+      class_linker->FindSystemClass(self, "Ljava/lang/Integer$IntegerCache;").Ptr();
   if (info.integer_cache == nullptr) {
     self->ClearException();
     return info;
@@ -281,7 +282,7 @@
     // Optimization only works if the class is initialized and in the boot image.
     return info;
   }
-  info.integer = class_linker->FindSystemClass(self, "Ljava/lang/Integer;");
+  info.integer = class_linker->FindSystemClass(self, "Ljava/lang/Integer;").Ptr();
   if (info.integer == nullptr) {
     self->ClearException();
     return info;