Improve Editor Inspector/Theme item lookup performance

Changes to reduce the latency between changing node selection in the editor and seeing the new node reflected in the Inspector tab

- Use Vector instead of List for ThemeOwner::get_theme_type_dependencies and related functions
- Use Vector instead of List for ThemeContext::themes, set_themes(), and get_themes()
- Add ClassDB:get_inheritance_chain_nocheck to get all parent/ancestor classes at once, to avoid repeated ClassDB locking overhead
- Update BIND_THEME_ITEM macros and ThemeDB::update_class_instance_items to use provided StringNames for call to ThemeItemSetter, instead of creating a new StringName in each call

These changes reduce the time taken by EditorInspector::update_tree by around 30-35%

core/object/class_db.cpp

@@ -291,6 +291,29 @@ StringName ClassDB::get_parent_class_nocheck(const StringName &p_class) {
 	return ti->inherits;
 }
 
+bool ClassDB::get_inheritance_chain_nocheck(const StringName &p_class, Vector<StringName> &r_result) {
+	OBJTYPE_RLOCK;
+
+	ClassInfo *start = classes.getptr(p_class);
+	if (!start) {
+		return false;
+	}
+
+	int classes_to_add = 0;
+	for (ClassInfo *ti = start; ti; ti = ti->inherits_ptr) {
+		classes_to_add++;
+	}
+
+	int64_t old_size = r_result.size();
+	r_result.resize(old_size + classes_to_add);
+	StringName *w = r_result.ptrw() + old_size;
+	for (ClassInfo *ti = start; ti; ti = ti->inherits_ptr) {
+		*w++ = ti->name;
+	}
+
+	return true;
+}
+
 StringName ClassDB::get_compatibility_remapped_class(const StringName &p_class) {
 	if (classes.has(p_class)) {
 		return p_class;