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-command/src/debug/view_files.rs

@@ -1,7 +1,7 @@
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Type, Value,
+    record, Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Type, Value,
 };
 
 #[derive(Clone)]
@@ -36,21 +36,15 @@ impl Command for ViewFiles {
         let mut records = vec![];
 
         for (file, start, end) in engine_state.files() {
-            records.push(Value::Record {
-                cols: vec![
-                    "filename".to_string(),
-                    "start".to_string(),
-                    "end".to_string(),
-                    "size".to_string(),
-                ],
-                vals: vec![
-                    Value::string(file, call.head),
-                    Value::int(*start as i64, call.head),
-                    Value::int(*end as i64, call.head),
-                    Value::int(*end as i64 - *start as i64, call.head),
-                ],
-                span: call.head,
-            });
+            records.push(Value::record(
+                record! {
+                    "filename" => Value::string(file, call.head),
+                    "start" => Value::int(*start as i64, call.head),
+                    "end" => Value::int(*end as i64, call.head),
+                    "size" => Value::int(*end as i64 - *start as i64, call.head),
+                },
+                call.head,
+            ));
         }
 
         Ok(Value::List {