ART: Convert pointer size to enum

Move away from size_t to dedicated enum (class).

Bug: 30373134
Bug: 30419309
Test: m test-art-host
Change-Id: Id453c330f1065012e7d4f9fc24ac477cc9bb9269
diff --git a/runtime/image.cc b/runtime/image.cc
index 2362a92..6888183 100644
--- a/runtime/image.cc
+++ b/runtime/image.cc
@@ -160,7 +160,7 @@
 
 void ImageHeader::VisitPackedArtMethods(ArtMethodVisitor* visitor,
                                         uint8_t* base,
-                                        size_t pointer_size) const {
+                                        PointerSize pointer_size) const {
   const size_t method_alignment = ArtMethod::Alignment(pointer_size);
   const size_t method_size = ArtMethod::Size(pointer_size);
   const ImageSection& methods = GetMethodsSection();