chore: bump Rust edition to 2024 and apply cargo fix + clippy updates

Run `cargo fix --edition` and resolve resulting warnings:

- Add `use<>` syntax to `impl Trait` return types (auto-fixed)
- Fix Rust 2024 temporary drop order change by simplifying `_initial_reconcile_rx` handling

Author: Saul-STFC

Cargo.nix

@@ -6,7 +6,7 @@ resolver = "2"
 version = "0.0.0-dev"
 authors = ["Stackable GmbH <info@stackable.tech>"]
 license = "OSL-3.0"
-edition = "2021"
+edition = "2024"
 repository = "https://github.com/stackabletech/kafka-operator"
 
 [workspace.dependencies]

Cargo.toml

@@ -92,7 +92,7 @@ pub fn build_discovery_configmap(
 fn listener_hosts(
     listeners: &[listener::v1alpha1::Listener],
     port_name: &str,
-) -> Result<impl IntoIterator<Item = (String, u16)>, Error> {
+) -> Result<impl IntoIterator<Item = (String, u16)> + use<>, Error> {
     listeners
         .iter()
         .flat_map(|listener| {

rust/operator-binary/src/discovery.rs

@@ -37,7 +37,7 @@ pub async fn create_webhook_server(
         field_manager: FIELD_MANAGER.to_owned(),
     };
 
-    let (conversion_webhook, _initial_reconcile_rx) =
+    let (conversion_webhook, _) =
         ConversionWebhook::new(crds_and_handlers, client, conversion_webhook_options);
 
     let webhook_server_options = WebhookServerOptions {