Remove some unnecessary static Vecs (#11947)

Avoid unnecessary allocations or larger iterator structs

- Turn static `Vec`s into arrays when possible
- Use `std::iter::once`/`empty` where applicable
- Use `bool::then_some` in `detect column` `.chain`
- Drop in the bucket: de-vec-ing tests

crates/nu-protocol/src/pipeline_data.rs

@@ -605,7 +605,7 @@ impl PipelineData {
                     .map(|bytes| bytes.item)
                     .unwrap_or_default();
                 RawStream::new(
-                    Box::new(vec![Ok(stderr_bytes)].into_iter()),
+                    Box::new(std::iter::once(Ok(stderr_bytes))),
                     stderr_ctrlc,
                     stderr_span,
                     None,