allow select to stream more (#14492)

# Description

closes https://github.com/nushell/nushell/issues/14487

This PR tries to allow the `select` to stream better by changing the for
loops that collected the output into a `Vec<Value>` prior to returning
it into a map that returns the data as it is processed.

One curiosity, `select` transforms the input into a `PipelineIterator`.
If I remove this code, it still passes all tests. I'm not sure all this
`PipelineIterator` code is even needed. I left it for someone to tell me
if it's necessary.

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

@@ -63,7 +63,7 @@ fn complex_nested_columns() {
 fn fails_if_given_unknown_column_name() {
     let actual = nu!(pipeline(
         r#"
-            echo [
+            [
                 [first_name, last_name, rusty_at, type];
 
                 [Andrés Robalino '10/11/2013' A]
@@ -71,7 +71,6 @@ fn fails_if_given_unknown_column_name() {
                 [Yehuda Katz '10/11/2013' A]
             ]
             | select rrusty_at first_name
-            | length
         "#
     ));