Use rust str instead of cstr in ClassIdSource

[beicause]

This simplifies things and improves performance of ClassId::to_cow_str, which is overhead in CallContext::gd and check_rtti.

#[bench(repeat = 10000)]
fn class_id_str() -> std::borrow::Cow<'static, str> {
    godot::classes::Object::class_id().to_cow_str()
}

// In debug build
// before:
//    -- class_id_str               ...      0.148μs      0.156μs
// after:
//    -- class_id_str               ...      0.119μs      0.125μs

I think the only reason for using cstr might be initializing StringName from it is slightly faster than rust str, but this is not a hot path since initialization only happens once.

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-1334

[Bromeon]

Thank you, nice simplification! 🙂

[beicause]

Clippy CI failed strangely, but I can't reproduce it locally.

[Yarwin]

it is because the file in question is formatted differently on CI (it is oooneee big line). Why? No idea (details of macro formatting are black magic to me, sorry 🤷).

Code in question as it is formatted on mine and beicause's sides

    #[func]
    fn check_last_notrace(last_method_name: String, expected_callconv: String) -> bool {
        let last = godot::private::trace::pop();
        let mut ok = true;
        if last.class != "GenFfi" {
            godot_error!("Expected class GenFfi, got {}", last.class);
            ok = false;
        }
        if last.method != last_method_name {
            godot_error!("Expected method {}, got {}", last_method_name, last.method);
            ok = false;
        }
        if !last.is_inbound {
            godot_error!("Expected inbound call, got outbound");
            ok = false;
        }
        let expect_ptrcall = expected_callconv == "ptrcall";
        if last.is_ptrcall != expect_ptrcall {
            let actual = Self::to_string(last.is_ptrcall);
            godot_error!("Expected {expected_callconv}, got {actual}");
            ok = false;
        }
        ok
    }

To elaborate, this code:

fn check(a: bool, b: bool, c: bool) -> bool {
    let mut godot_error = false;
    if a {
        println!("a");
        godot_error = true;
    }
    if b {
        println!("b");
        godot_error = true;
    }
    if c {
        println!("c");
        godot_error = true;
    }
    godot_error
}

is fine and triggers no clippy warnings, meanwhile

fn check(a: bool, b: bool, c: bool) -> bool {
    let mut godot_error = false;
    if a {
        println!("a");
        godot_error = true;
    } if b {
        println!("b");
        godot_error = true;
    }
    if c {
        println!("c");
        godot_error = true;
    }
    godot_error
}

triggers following warning:

    Checking playground v0.0.1 (/playground)
warning: this looks like an `else if` but the `else` is missing
 --> src/main.rs:6:6
  |
6 |     } if b {
  |      ^
  |
  = note: to remove this lint, add the missing `else` or add a new line before the second `if`
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_else_formatting
  = note: `#[warn(clippy::suspicious_else_formatting)]` on by default

[Yarwin]

EDIT: I'll address it, in this case simple #[allow(...)] will be fine