Default strings and vectors: Parser + Rust support (#6421)

* Fix tests.cpp

* Parser support for vector/string defaults

* tests and default empty vectors

* addressed comments

* Default strings and vectors for Rust

* Tested Rust more_defaults

* git-clang-format

* add more_defaults_test

* fixed vector default

* removed commented out code

* more unreachable

Co-authored-by: Casper Neo <cneo@google.com>

tests/monster_test_generated.rs

@@ -3197,7 +3197,7 @@ impl Default for MonsterT {
       pos: None,
       mana: 150,
       hp: 100,
-      name: String::new(),
+      name: "".to_string(),
       inventory: None,
       color: Color::Blue,
       test: AnyT::NONE,