Single argument function calls dont work.

Nobody has claimed this yet.

On Main branch calling with a single argument tuple or single argument in either direction doesn't work.

Calling Rust from Lua

```
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_scripting::(|runtime| {
runtime.add_function(String::from("func_with_params"), |In((a)): In<(i64)>| {
//doesnt compile trait bounds not satisfied.
});
})
.run();
}
```

Calling Lua from Rust
```
fn call_lua_on_update_from_rust(
mut scripted_entities: Query<(Entity, &mut LuaScriptData)>,
scripting_runtime: ResMut,
) {
for (entity, mut script_data) in &mut scripted_entities {
scripting_runtime
.call_fn("on_update", &mut script_data, entity, (123)) //FuncArgs not satisfied
.unwrap();
}
}

function on_update(a)
print(a) -- 123
end

```

Calling Lua from Rust will work if I replace the single argument tuple with a vec e.g. vec![123]

Start by reproducing both examples on the Main branch: Rust-to-Lua registration through add_function and Lua-to-Rust calls through call_fn. Read the FuncArgs implementations and related argument-conversion entry points. Done means a single scalar and a one-element tuple work in both directions, while existing vector calls continue to work.

Written by the indexing model from the issue text.