Remove mirror::String::java_lang_String_.

And simplify ClassLinker::InitWithoutImage().
And finish ObjPtr<>-ification of annotation processing.

Test: m test-art-host-gtest
Test: testrunner.py --host
Bug: 31113334
Change-Id: I882a6c2f2b2a88d6ba34e4759bac4a6caa54cafa
diff --git a/openjdkjvmti/ti_field.cc b/openjdkjvmti/ti_field.cc
index 328e2a1..2a860d9 100644
--- a/openjdkjvmti/ti_field.cc
+++ b/openjdkjvmti/ti_field.cc
@@ -91,7 +91,7 @@
   if (generic_ptr != nullptr) {
     *generic_ptr = nullptr;
     if (!art_field->GetDeclaringClass()->IsProxyClass()) {
-      art::mirror::ObjectArray<art::mirror::String>* str_array =
+      art::ObjPtr<art::mirror::ObjectArray<art::mirror::String>> str_array =
           art::annotations::GetSignatureAnnotationForField(art_field);
       if (str_array != nullptr) {
         std::ostringstream oss;