Add spacetime_worker_sender_errors_total metric

Currently we have a metric for reducer panics called
`spacetime_worker_wasm_instance_errors_total`. This commit adds a
metric for tracking errors returned from the module, like for example an
Err result in Rust, or throwing a SenderError in TypeScript

Author: drogus

crates/core/src/host/wasm_common/module_host_actor.rs

@@ -643,6 +643,10 @@ impl InstanceCommon {
             }) {
                 Ok(()) => EventStatus::Committed(DatabaseUpdate::default()),
                 Err(err) => {
+                    WORKER_METRICS
+                        .wasm_instance_sender_errors
+                        .with_label_values(&database_identity, &self.info.module_hash, reducer_name)
+                        .inc();
                     log::info!("reducer returned error: {err}");
                     log_reducer_error(replica_ctx, timestamp, reducer_name, &err);
                     EventStatus::Failed(err.into())

crates/core/src/worker_metrics/mod.rs

@@ -246,6 +246,11 @@ metrics_group!(
         #[labels(caller_identity: Identity, module_hash: Hash, caller_connection_id: ConnectionId, reducer_symbol: str)]
         pub wasm_instance_errors: IntCounterVec,
 
+        #[name = spacetime_worker_wasm_instance_sender_errors_total]
+        #[help = "The number of sender errors returned from reducers."]
+        #[labels(database_identity: Identity, module_hash: Hash, reducer_symbol: str)]
+        pub wasm_instance_sender_errors: IntCounterVec,
+
         #[name = spacetime_worker_wasm_memory_bytes]
         #[help = "The number of bytes of linear memory allocated by the database's WASM module instance"]
         #[labels(database_identity: Identity)]