ART: Change return types of field access entrypoints

Ensure that return types guarantee full-width data as the compiled
code and mterp expect by using size_t and ssize_t.

This fixes Clang no longer sign-/zero-extending small return types.

Bug: 30232671
Test: m ART_TEST_RUN_TEST_NDEBUG=true ART_TEST_INTERPRETER=true test-art-host-run-test
Change-Id: Ic505befc6c94e2dccbc8abf2b13d4c2d662e68d1
diff --git a/runtime/entrypoints/quick/quick_cast_entrypoints.cc b/runtime/entrypoints/quick/quick_cast_entrypoints.cc
index 968ac53..8db69a3 100644
--- a/runtime/entrypoints/quick/quick_cast_entrypoints.cc
+++ b/runtime/entrypoints/quick/quick_cast_entrypoints.cc
@@ -20,7 +20,7 @@
 namespace art {
 
 // Assignable test for code, won't throw.  Null and equality tests already performed
-extern "C" uint32_t artIsAssignableFromCode(mirror::Class* klass, mirror::Class* ref_class)
+extern "C" size_t artIsAssignableFromCode(mirror::Class* klass, mirror::Class* ref_class)
     SHARED_REQUIRES(Locks::mutator_lock_) {
   DCHECK(klass != nullptr);
   DCHECK(ref_class != nullptr);