Everywhere: Add deprecated_ prefix to JsonValue::to_byte_string

`JsonValue::to_byte_string` has peculiar type-erasure semantics which is
not usually intended. Unfortunately, it also has a very stereotypical
name which does not warn about unexpected behavior. So let's prefix it
with `deprecated_` to make new code use `as_string` if it just wants to
get string value or `serialized<StringBuilder>` if it needs to do proper
serialization.

Userland/Libraries/LibGUI/DynamicWidgetContainer.cpp

@@ -144,7 +144,7 @@ void DynamicWidgetContainer::restore_view_state()
 
             order_or_error.value().as_array().for_each([&](auto& section_label) {
                 for (auto& container : containers) {
-                    if (container.section_label() == section_label.to_byte_string())
+                    if (container.section_label() == section_label.as_string())
                         new_child_order.append(container);
                 }
             });