feature: CancellationToken-based shutdowns (#5325)

* initial stub for ShutdownToken

* attempting to start using new ShutdownManager in NymNode

* migrated verloc tasks

* added custom shutdown signal registration

* integrated legacy task support

* migrated additional tasks inside nym-node

* removed import thats unused in wasm

* apply review comments

* windows fixes

nym-node/src/error.rs

@@ -50,6 +50,12 @@ pub enum NymNodeError {
     #[error("this binary version no longer supports migration from legacy mixnodes and gateways")]
     UnsupportedMigration,
 
+    #[error("failed to initialise shutdown signals: {source}")]
+    ShutdownSignalFailure {
+        #[source]
+        source: io::Error,
+    },
+
     #[error("could not find an existing config file at '{}' and fresh node initialisation has been disabled", config_path.display())]
     ForbiddenInitialisation { config_path: PathBuf },