Add wchar support (#349)

* Add wchar support and .idl example

* Undo automatic IDE formatting noise

* Added back unused imports to see if this fixes the build

* More attempts to fix the weird build failure

* Removed the linter tests for auto-generated message source files in `rclrs_example_msgs`. Re-applied some changes removed when root causing.

---------

Co-authored-by: Sam Privett <sam@privett.dev>

Author: maspe36

rclrs/message_demo/src/message_demo.rs

@@ -68,6 +68,14 @@ fn check_default_values() {
     );
 }
 
+fn check_default_idl_values() {
+    let idiomatic_msg = rclrs_example_msgs::msg::MyMessage::default();
+    let rmw_msg = rclrs_example_msgs::msg::rmw::MyMessage::default();
+
+    assert_eq!(idiomatic_msg.wchar_value, 0u16);
+    assert_eq!(rmw_msg.wchar_value, 0u16);
+}
+
 fn demonstrate_printing() {
     let default_msg = rclrs_example_msgs::msg::VariousTypes::default();
     println!("================== Compact debug representation ==================");
@@ -170,6 +178,7 @@ fn demonstrate_pubsub() -> Result<(), Error> {
 
 fn main() -> Result<(), Error> {
     check_default_values();
+    check_default_idl_values();
     demonstrate_printing();
     demonstrate_serde()?;
     demonstrate_sequences();