[vm] Add HANDLESCOPE in KernelLoader::LoadLibrary

This reduces amount of handles and live data kept around
after each library is loaded which helps on large
apps.

TEST=ci

Cq-Include-Trybots: luci.dart.try:vm-aot-linux-debug-x64-try,vm-aot-linux-debug-x64c-try,vm-linux-debug-x64-try,vm-linux-debug-x64c-try,vm-mac-debug-arm64-try,vm-mac-debug-x64-try
Change-Id: I9ae8f31a5912c589b4668f0937e4744315c21d19
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420321
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Slava Egorov <[email protected]>

Author: mraleph

runtime/vm/compiler/frontend/kernel_translation_helper.h

@@ -199,7 +199,8 @@ class TranslationHelper {
 
   void SetExpressionEvaluationFunction(const Function& function) {
     ASSERT(expression_evaluation_function_ == nullptr);
-    expression_evaluation_function_ = &Function::Handle(zone_, function.ptr());
+    expression_evaluation_function_ =
+        &Function::ZoneHandle(zone_, function.ptr());
   }
   const Function& GetExpressionEvaluationFunction() {
     if (expression_evaluation_function_ == nullptr) {
@@ -210,7 +211,7 @@ class TranslationHelper {
   void SetExpressionEvaluationClass(const Class& cls) {
     ASSERT(expression_evaluation_class_ == nullptr);
     ASSERT(!cls.IsNull());
-    expression_evaluation_class_ = &Class::Handle(zone_, cls.ptr());
+    expression_evaluation_class_ = &Class::ZoneHandle(zone_, cls.ptr());
   }
   const Class& GetExpressionEvaluationClass() {
     if (expression_evaluation_class_ == nullptr) {
@@ -221,7 +222,8 @@ class TranslationHelper {
   void SetExpressionEvaluationRealClass(const Class& real_class) {
     ASSERT(expression_evaluation_real_class_ == nullptr);
     ASSERT(!real_class.IsNull());
-    expression_evaluation_real_class_ = &Class::Handle(zone_, real_class.ptr());
+    expression_evaluation_real_class_ =
+        &Class::ZoneHandle(zone_, real_class.ptr());
   }
   const Class& GetExpressionEvaluationRealClass() {
     if (expression_evaluation_real_class_ == nullptr) {

runtime/vm/kernel_loader.cc

@@ -790,6 +790,7 @@ void KernelLoader::CheckForInitializer(const Field& field) {
 }
 
 LibraryPtr KernelLoader::LoadLibrary(intptr_t index) {
+  HANDLESCOPE(thread_);
   if (!program_->is_single_program()) {
     FATAL(
         "Trying to load a concatenated dill file at a time where that is "