Create Record type (#10103)

# Description
This PR creates a new `Record` type to reduce duplicate code and
possibly bugs as well. (This is an edited version of #9648.)
- `Record` implements `FromIterator` and `IntoIterator` and so can be
iterated over or collected into. For example, this helps with
conversions to and from (hash)maps. (Also, no more
`cols.iter().zip(vals)`!)
- `Record` has a `push(col, val)` function to help insure that the
number of columns is equal to the number of values. I caught a few
potential bugs thanks to this (e.g. in the `ls` command).
- Finally, this PR also adds a `record!` macro that helps simplify
record creation. It is used like so:
   ```rust
   record! {
       "key1" => some_value,
       "key2" => Value::string("text", span),
       "key3" => Value::int(optional_int.unwrap_or(0), span),
       "key4" => Value::bool(config.setting, span),
   }
   ```
Since macros hinder formatting, etc., the right hand side values should
be relatively short and sweet like the examples above.

Where possible, prefer `record!` or `.collect()` on an iterator instead
of multiple `Record::push`s, since the first two automatically set the
record capacity and do less work overall.

# User-Facing Changes
Besides the changes in `nu-protocol` the only other breaking changes are
to `nu-table::{ExpandedTable::build_map, JustTable::kv_table}`.

crates/nu-cmd-dataframe/src/dataframe/values/nu_dataframe/conversion.rs

@@ -2,7 +2,7 @@ use super::{DataFrameValue, NuDataFrame};
 
 use chrono::{DateTime, FixedOffset, NaiveDateTime};
 use indexmap::map::{Entry, IndexMap};
-use nu_protocol::{ShellError, Span, Value};
+use nu_protocol::{Record, ShellError, Span, Value};
 use polars::chunked_array::builder::AnonymousOwnedListBuilder;
 use polars::chunked_array::object::builder::ObjectChunkedBuilder;
 use polars::chunked_array::ChunkedArray;
@@ -128,36 +128,21 @@ pub fn create_column(
 // Adds a separator to the vector of values using the column names from the
 // dataframe to create the Values Row
 pub fn add_separator(values: &mut Vec<Value>, df: &DataFrame, span: Span) {
-    let mut cols = vec![];
-    let mut vals = vec![];
+    let mut record = Record::new();
 
-    cols.push("index".to_string());
-    vals.push(Value::String {
-        val: "...".into(),
-        span,
-    });
+    record.push("index", Value::string("...", span));
 
     for name in df.get_column_names() {
-        cols.push(name.to_string());
-        vals.push(Value::String {
-            val: "...".into(),
-            span,
-        })
+        record.push(name, Value::string("...", span))
     }
 
-    let extra_record = Value::Record { cols, vals, span };
-
-    values.push(extra_record);
+    values.push(Value::record(record, span));
 }
 
-// Inserting the values found in a Value::List
-pub fn insert_record(
-    column_values: &mut ColumnMap,
-    cols: &[String],
-    values: &[Value],
-) -> Result<(), ShellError> {
-    for (col, value) in cols.iter().zip(values.iter()) {
-        insert_value(value.clone(), col.clone(), column_values)?;
+// Inserting the values found in a Value::List or Value::Record
+pub fn insert_record(column_values: &mut ColumnMap, record: Record) -> Result<(), ShellError> {
+    for (col, value) in record {
+        insert_value(value, col, column_values)?;
     }
 
     Ok(())

crates/nu-cmd-dataframe/src/dataframe/values/nu_dataframe/mod.rs

@@ -7,7 +7,7 @@ pub use conversion::{Column, ColumnMap};
 pub use operations::Axis;
 
 use indexmap::map::IndexMap;
-use nu_protocol::{did_you_mean, PipelineData, ShellError, Span, Value};
+use nu_protocol::{did_you_mean, PipelineData, Record, ShellError, Span, Value};
 use polars::prelude::{DataFrame, DataType, IntoLazy, LazyFrame, PolarsObject, Series};
 use serde::{Deserialize, Serialize};
 use std::{cmp::Ordering, fmt::Display, hash::Hasher};
@@ -162,10 +162,10 @@ impl NuDataFrame {
                         .map(|i| format!("{i}"))
                         .collect::<Vec<String>>();
 
-                    conversion::insert_record(&mut column_values, &cols, &vals)?
+                    conversion::insert_record(&mut column_values, Record { cols, vals })?
                 }
-                Value::Record { cols, vals, .. } => {
-                    conversion::insert_record(&mut column_values, &cols, &vals)?
+                Value::Record { val: record, .. } => {
+                    conversion::insert_record(&mut column_values, record)?
                 }
                 _ => {
                     let key = "0".to_string();
@@ -427,25 +427,15 @@ impl NuDataFrame {
 
         let values = (0..size)
             .map(|i| {
-                let mut cols = vec![];
-                let mut vals = vec![];
+                let mut record = Record::new();
 
-                cols.push("index".into());
-                vals.push(Value::Int {
-                    val: (i + from_row) as i64,
-                    span,
-                });
+                record.push("index", Value::int((i + from_row) as i64, span));
 
                 for (name, col) in &mut iterators {
-                    cols.push(name.clone());
-
-                    match col.next() {
-                        Some(v) => vals.push(v),
-                        None => vals.push(Value::Nothing { span }),
-                    };
+                    record.push(name.clone(), col.next().unwrap_or(Value::nothing(span)));
                 }
 
-                Value::Record { cols, vals, span }
+                Value::record(record, span)
             })
             .collect::<Vec<Value>>();