Feature/cancellation migration (#6014)

* squashing work on using cancellation in nym crates

making nym-task wasm compilable

removed sending of status messages

replaced TaskManager with ShutdownManager in the validator rewarder

additional helpers for ShutdownManager

simplified ShutdownToken by removing the name field

TaskClient => ShutdownToken within all client tasks

wip: remove TaskHandle

* track all long-living client tasks

* add task tracking for most top level tasks within nym-node

* improved default builder

* split up cancellation module

* module documentation and unit tests

* nym node fixes and naming consistency

* wasm fixes

* assert_eq => assert

* wasm fixes and made 'run_until_shutdown' take reference instead of ownership

* linux-specific fixes to IpPacketRouter

* post rebasing fixes for signing monitor

* add ShutdownManager constructor to build it from an external token

* applying PR review suggestions

nym-signers-monitor/src/monitor.rs

@@ -190,15 +190,15 @@ impl SignersMonitor {
     }
 
     pub(crate) async fn run(&mut self) -> anyhow::Result<()> {
-        let shutdown_manager =
-            ShutdownManager::new("nym-signers-monitor").with_default_shutdown_signals()?;
+        let mut shutdown_manager = ShutdownManager::build_new_default()?;
+        let root_token = shutdown_manager.clone_shutdown_token();
 
         let mut check_interval = interval(self.check_interval);
 
-        while !shutdown_manager.root_token.is_cancelled() {
+        while !root_token.is_cancelled() {
             tokio::select! {
                 biased;
-                _ = shutdown_manager.root_token.cancelled() => {
+                _ = root_token.cancelled() => {
                     info!("received shutdown");
                     break;
                 }
@@ -211,7 +211,6 @@ impl SignersMonitor {
             }
         }
 
-        shutdown_manager.close();
         shutdown_manager.run_until_shutdown().await;
 
         if let Err(err) = self.send_shutdown_notification().await {