Name threads (#7879)

I noticed that [it's pretty easy to name threads in
Rust](https://doc.rust-lang.org/std/thread/#naming-threads). We might as
well do this; it's a nice quality of life improvement when you're
profiling something and the developers took the time to give threads
names.

Also added/cleaned up some comments while I was in the area.

crates/nu-protocol/src/pipeline_data.rs

@@ -5,6 +5,7 @@ use crate::{
 };
 use nu_utils::{stderr_write_all_and_flush, stdout_write_all_and_flush};
 use std::sync::{atomic::AtomicBool, Arc};
+use std::thread;
 
 const LINE_ENDING_PATTERN: &[char] = &['\r', '\n'];
 
@@ -726,8 +727,11 @@ pub fn print_if_stream(
     exit_code: Option<ListStream>,
 ) -> Result<i64, ShellError> {
     // NOTE: currently we don't need anything from stderr
-    // so directly consumes `stderr_stream` to make sure that everything is done.
-    std::thread::spawn(move || stderr_stream.map(|x| x.into_bytes()));
+    // so we just consume and throw away `stderr_stream` to make sure the pipe doesn't fill up
+    thread::Builder::new()
+        .name("stderr consumer".to_string())
+        .spawn(move || stderr_stream.map(|x| x.into_bytes()))
+        .expect("could not create thread");
     if let Some(stream) = stream {
         for s in stream {
             let s_live = s?;