Reland "Change well known `ClassLoader` fields to `ArtField*`."

This reverts commit 839193ee2031d28aac2ce16c4b76ad40531b07cc.

Reason for revert: Reland with a fix - make CompilerDriver
reponsible for initializing required `ClassLoader` classes
for boot image.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: Manually run Golem benchmark ArrayListStress.
Bug: 253570082
Change-Id: I2ddb70566352f8728f089b3a6c58473270240e25
diff --git a/runtime/class_loader_utils.h b/runtime/class_loader_utils.h
index c777370..aabc4ca 100644
--- a/runtime/class_loader_utils.h
+++ b/runtime/class_loader_utils.h
@@ -82,13 +82,11 @@
     REQUIRES_SHARED(Locks::mutator_lock_) {
   Thread* self = soa.Self();
   ObjPtr<mirror::Object> dex_path_list =
-      jni::DecodeArtField(WellKnownClasses::dalvik_system_BaseDexClassLoader_pathList)->
-          GetObject(class_loader.Get());
+      WellKnownClasses::dalvik_system_BaseDexClassLoader_pathList->GetObject(class_loader.Get());
   if (dex_path_list != nullptr) {
     // DexPathList has an array dexElements of Elements[] which each contain a dex file.
     ObjPtr<mirror::Object> dex_elements_obj =
-        jni::DecodeArtField(WellKnownClasses::dalvik_system_DexPathList_dexElements)->
-            GetObject(dex_path_list);
+        WellKnownClasses::dalvik_system_DexPathList_dexElements->GetObject(dex_path_list);
     // Loop through each dalvik.system.DexPathList$Element's dalvik.system.DexFile and look
     // at the mCookie which is a DexFile vector.
     if (dex_elements_obj != nullptr) {
@@ -122,10 +120,8 @@
                                         Visitor fn,
                                         RetType defaultReturn)
     REQUIRES_SHARED(Locks::mutator_lock_) {
-  ArtField* const cookie_field =
-      jni::DecodeArtField(WellKnownClasses::dalvik_system_DexFile_cookie);
-  ArtField* const dex_file_field =
-      jni::DecodeArtField(WellKnownClasses::dalvik_system_DexPathList__Element_dexFile);
+  ArtField* const cookie_field = WellKnownClasses::dalvik_system_DexFile_cookie;
+  ArtField* const dex_file_field = WellKnownClasses::dalvik_system_DexPathList__Element_dexFile;
   if (dex_file_field == nullptr || cookie_field == nullptr) {
     return defaultReturn;
   }