[cleanup] Add helpers/use existing ones more in bootstrapper

This CL makes several changes to bootstrapper to reduce
code verbosity:

  - Adds an InstallToStringTag helper and uses it everywhere (while
    removing now-redundant comments).
  - Reduces explicit calls to Factory::InternalizeUtf8String
    by adding some overloads of helpers and of JSObject::AddProperty.
  - Uses InstallConstant in all applicable cases.
  - Removes attributes arguments when all callers pass DONT_ENUM.

Change-Id: Ifb5f5102f5fbf89d475045270eeda78a2ee99248
Reviewed-on: https://chromium-review.googlesource.com/c/1385526Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58413}

src/objects.cc

@@ -6450,6 +6450,13 @@ void JSObject::AddProperty(Isolate* isolate, Handle<JSObject> object,
             .IsJust());
 }
 
+void JSObject::AddProperty(Isolate* isolate, Handle<JSObject> object,
+                           const char* name, Handle<Object> value,
+                           PropertyAttributes attributes) {
+  JSObject::AddProperty(isolate, object,
+                        isolate->factory()->InternalizeUtf8String(name), value,
+                        attributes);
+}
 
 // Reconfigures a property to a data property with attributes, even if it is not
 // reconfigurable.

src/objects/js-objects.h

@@ -408,6 +408,11 @@ class JSObject : public JSReceiver {
                           Handle<Name> name, Handle<Object> value,
                           PropertyAttributes attributes);
 
+  // {name} must be a UTF-8 encoded, null-terminated string.
+  static void AddProperty(Isolate* isolate, Handle<JSObject> object,
+                          const char* name, Handle<Object> value,
+                          PropertyAttributes attributes);
+
   static void AddDataElement(Handle<JSObject> receiver, uint32_t index,
                              Handle<Object> value,
                              PropertyAttributes attributes);