ListStream touchup (#12524)

# Description

Does some misc changes to `ListStream`:
- Moves it into its own module/file separate from `RawStream`.
- `ListStream`s now have an associated `Span`.
- This required changes to `ListStreamInfo` in `nu-plugin`. Note sure if
this is a breaking change for the plugin protocol.
- Hides the internals of `ListStream` but also adds a few more methods.
- This includes two functions to more easily alter a stream (these take
a `ListStream` and return a `ListStream` instead of having to go through
the whole `into_pipeline_data(..)` route).
  -  `map`: takes a `FnMut(Value) -> Value`
  - `modify`: takes a function to modify the inner stream.

crates/nu-command/src/math/utils.rs

@@ -69,7 +69,7 @@ pub fn calculate(
     let span = values.span().unwrap_or(name);
     match values {
         PipelineData::ListStream(s, ..) => {
-            helper_for_tables(&s.collect::<Vec<Value>>(), span, name, mf)
+            helper_for_tables(&s.into_iter().collect::<Vec<Value>>(), span, name, mf)
         }
         PipelineData::Value(Value::List { ref vals, .. }, ..) => match &vals[..] {
             [Value::Record { .. }, _end @ ..] => helper_for_tables(