[Rust] Ensure unions are referenced with the correct path (#6422)

* Add codegen test for namespaced unions

* [Rust] Handle cross-namespace union use

* [Rust] Test namespace handling

* [Rust] Drop trailing whitespace in codegen

* [Rust] Set flags in generate_code.bat to match .sh

* [C#] Add additional namespace test file

samples/monster_generated.rs

@@ -212,7 +212,7 @@ impl Default for EquipmentT {
   }
 }
 impl EquipmentT {
-  fn equipment_type(&self) -> Equipment {
+  pub fn equipment_type(&self) -> Equipment {
     match self {
       Self::NONE => Equipment::NONE,
       Self::Weapon(_) => Equipment::Weapon,
@@ -689,7 +689,7 @@ impl std::fmt::Debug for Monster<'_> {
             ds.field("equipped", &"InvalidFlatbuffer: Union discriminant does not match value.")
           }
         },
-        _ => { 
+        _ => {
           let x: Option<()> = None;
           ds.field("equipped", &x)
         },