Improve CellPath display output (#14197)

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# Description
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Fixes: #13362

This PR fixes the `Display` impl for `CellPath`, as laid out in #13362
and #14090:

```nushell
> $.0."0"
$.0."0"

> $."foo.bar".baz
$."foo.bar".baz
```

# User-Facing Changes
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helps us keep track of breaking changes. -->

Cell-paths are now printed using the same `$.` notation that is used to
create them, and ambiguous column names are properly quoted.

# Tests + Formatting
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crates/nu-command/tests/commands/reject.rs

@@ -130,7 +130,10 @@ fn reject_optional_row() {
 #[test]
 fn reject_columns_with_list_spread() {
     let actual = nu!("let arg = [type size]; [[name type size];[Cargo.toml file 10mb] [Cargo.lock file 10mb] [src dir 100mb]] | reject ...$arg | to nuon");
-    assert_eq!(actual.out, "[[name]; [Cargo.toml], [Cargo.lock], [src]]");
+    assert_eq!(
+        actual.out,
+        r#"[[name]; ["Cargo.toml"], ["Cargo.lock"], [src]]"#
+    );
 }
 
 #[test]
@@ -138,7 +141,7 @@ fn reject_rows_with_list_spread() {
     let actual = nu!("let arg = [2 0]; [[name type size];[Cargo.toml file 10mb] [Cargo.lock file 10mb] [src dir 100mb]] | reject ...$arg | to nuon");
     assert_eq!(
         actual.out,
-        "[[name, type, size]; [Cargo.lock, file, 10000000b]]"
+        r#"[[name, type, size]; ["Cargo.lock", file, 10000000b]]"#
     );
 }
 
@@ -147,7 +150,7 @@ fn reject_mixed_with_list_spread() {
     let actual = nu!("let arg = [type 2]; [[name type size];[Cargp.toml file 10mb] [ Cargo.lock file 10mb] [src dir 100mb]] | reject ...$arg | to nuon");
     assert_eq!(
         actual.out,
-        "[[name, size]; [Cargp.toml, 10000000b], [Cargo.lock, 10000000b]]"
+        r#"[[name, size]; ["Cargp.toml", 10000000b], ["Cargo.lock", 10000000b]]"#
     );
 }