Add utility background job test function

Author: cosineblast

crates/nu-command/src/env/config/config_.rs

@@ -106,7 +106,7 @@ pub(super) fn start_editor(
     let child = ForegroundChild::spawn(
         command,
         engine_state.is_interactive,
-        engine_state.current_thread_job.is_some(),
+        engine_state.is_background_job(),
         &engine_state.pipeline_externals_state,
     );
 

crates/nu-command/src/system/run_external.rs

@@ -251,7 +251,7 @@ impl Command for External {
         let child = ForegroundChild::spawn(
             command,
             engine_state.is_interactive,
-            engine_state.current_thread_job.is_some(),
+            engine_state.is_background_job(),
             &engine_state.pipeline_externals_state,
         );
 

crates/nu-protocol/src/engine/engine_state.rs

@@ -1072,6 +1072,11 @@ impl EngineState {
             .position(|sp| sp == &span)
             .map(SpanId::new)
     }
+
+    // Determines whether the current state is being held by a background job
+    pub fn is_background_job(&self) -> bool {
+        self.current_thread_job.is_some()
+    }
 }
 
 impl GetSpan for &EngineState {