Bubble up errors passed to complete (#11313)

Errors passed in `PipelineData::Value` get thrown in `complete` now.

Also added two simple tests for the command.

Fix #11187
Fix #10204

crates/nu-command/tests/commands/complete.rs

@@ -0,0 +1,17 @@
+use nu_test_support::nu;
+
+#[test]
+fn basic() {
+    let actual = nu!(r#"
+        (^echo a | complete) == {stdout: "a\n", exit_code: 0}
+    "#);
+
+    assert_eq!(actual.out, "true");
+}
+
+#[test]
+fn error() {
+    let actual = nu!("do { not-found } | complete");
+
+    assert!(actual.err.contains("executable was not found"));
+}