Move ArtField to ObjPtr

Added EXPECT_OBJ_PTR_EQ and variants to gtests.

Fixed moving GC bugs in:
ClassLinker::CreatePathClassLoader
ClassLinkerTest: StaticFields

ObjPtr Decode call sites: 186 -> 181.

Some tests fail due to ResolvedFieldAccessTest, will fix in follow
up CL.

Bug: 31113334

Test: test-art-host CC baker

Change-Id: I8b266ad00f3c20c8cbe7cfdf280d175083df0b88
diff --git a/runtime/mirror/class.cc b/runtime/mirror/class.cc
index 2e5f532..40742d2 100644
--- a/runtime/mirror/class.cc
+++ b/runtime/mirror/class.cc
@@ -308,9 +308,9 @@
   }
 }
 
-bool Class::IsInSamePackage(Class* that) {
-  Class* klass1 = this;
-  Class* klass2 = that;
+bool Class::IsInSamePackage(ObjPtr<Class> that) {
+  ObjPtr<Class> klass1 = this;
+  ObjPtr<Class> klass2 = that;
   if (klass1 == klass2) {
     return true;
   }