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/bytes/at.rs

@@ -4,7 +4,8 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::{Call, CellPath},
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, Range, ShellError, Signature, Span, SyntaxShape, Type, Value,
+    Category, Example, PipelineData, Range, Record, ShellError, Signature, Span, SyntaxShape, Type,
+    Value,
 };
 
 #[derive(Clone)]
@@ -109,10 +110,10 @@ impl Command for BytesAt {
             Example {
                 description: "Get the remaining characters from a starting index",
                 example: " { data: 0x[33 44 55 10 01 13] } | bytes at 3.. data",
-                result: Some(Value::test_record(
-                    vec!["data"],
-                    vec![Value::test_binary(vec![0x10, 0x01, 0x13])],
-                )),
+                result: Some(Value::test_record(Record {
+                    cols: vec!["data".to_string()],
+                    vals: vec![Value::test_binary(vec![0x10, 0x01, 0x13])],
+                })),
             },
             Example {
                 description: "Get the characters from the beginning until ending index",
@@ -127,7 +128,7 @@ impl Command for BytesAt {
                     "Or the characters from the beginning until ending index inside a table",
                 example: r#" [[ColA ColB ColC]; [0x[11 12 13] 0x[14 15 16] 0x[17 18 19]]] | bytes at 1.. ColB ColC"#,
                 result: Some(Value::List {
-                    vals: vec![Value::Record {
+                    vals: vec![Value::test_record(Record {
                         cols: vec!["ColA".to_string(), "ColB".to_string(), "ColC".to_string()],
                         vals: vec![
                             Value::Binary {
@@ -143,8 +144,7 @@ impl Command for BytesAt {
                                 span: Span::test_data(),
                             },
                         ],
-                        span: Span::test_data(),
-                    }],
+                    })],
                     span: Span::test_data(),
                 }),
             },