feat(table): add 'double' table mode (#16013)

# Description

Add 'double' table mode, that is similar to `compact_double` but with
left and right border lines. This is similar to how there exist both
`single` and `compact`, but there is no `double` to compliment
`compact_double`. Printing `[ { a: 1, b: 11 }, { a: 2, b:12 } ]` looks
like this:

```
╔═══╦═══╦════╗
║ # ║ a ║ b  ║
╠═══╬═══╬════╣
║ 0 ║ 1 ║ 11 ║
║ 1 ║ 2 ║ 12 ║
╚═══╩═══╩════╝
```

The implementation is mostly a one-to-one of #15672 and #15681.

# User-Facing Changes

New value `double` to set as `$env.config.table.mode`.

# Tests + Formatting

Tests are added following the example of adding 'single' mode.

# After Submitting

crates/nu-table/src/common.rs

@@ -187,6 +187,7 @@ pub fn load_theme(mode: TableMode) -> TableTheme {
         TableMode::AsciiRounded => TableTheme::ascii_rounded(),
         TableMode::BasicCompact => TableTheme::basic_compact(),
         TableMode::Single => TableTheme::single(),
+        TableMode::Double => TableTheme::double(),
     }
 }
 

crates/nu-table/src/table_theme.rs

@@ -166,6 +166,15 @@ impl TableTheme {
         Self::new(Style::sharp(), full)
     }
 
+    pub fn double() -> TableTheme {
+        let hline = HorizontalLine::inherit(Style::extended());
+        let theme = Style::extended()
+            .remove_horizontal()
+            .horizontals([(1, hline)]);
+
+        Self::new(theme, Style::extended())
+    }
+
     pub fn none() -> TableTheme {
         Self::new(Style::blank(), Style::blank())
     }

crates/nu-table/tests/style.rs

@@ -497,6 +497,52 @@ fn test_single() {
     assert_eq!(create_table_with_size(vec![], true, theme::single()), "");
 }
 
+#[test]
+fn test_double() {
+    assert_eq!(
+        create_table(vec![row(4); 3], true, theme::double()),
+        "╔═══╦═══╦═══╦═══╗\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╠═══╬═══╬═══╬═══╣\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╚═══╩═══╩═══╩═══╝"
+    );
+
+    assert_eq!(
+        create_table(vec![row(4); 2], true, theme::double()),
+        "╔═══╦═══╦═══╦═══╗\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╠═══╬═══╬═══╬═══╣\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╚═══╩═══╩═══╩═══╝"
+    );
+
+    assert_eq!(
+        create_table(vec![row(4); 1], true, theme::double()),
+        "╔═══╦═══╦═══╦═══╗\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╚═══╩═══╩═══╩═══╝"
+    );
+
+    assert_eq!(
+        create_table(vec![row(4); 1], false, theme::double()),
+        "╔═══╦═══╦═══╦═══╗\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╚═══╩═══╩═══╩═══╝"
+    );
+
+    assert_eq!(
+        create_table(vec![row(4); 2], false, theme::double()),
+        "╔═══╦═══╦═══╦═══╗\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ║ 0 ║ 1 ║ 2 ║ 3 ║\n\
+         ╚═══╩═══╩═══╩═══╝"
+    );
+
+    assert_eq!(create_table_with_size(vec![], true, theme::double()), "");
+}
+
 fn create_table(data: Vec<Vec<Text<String>>>, with_header: bool, theme: theme) -> String {
     let mut case = TestCase::new(usize::MAX).theme(theme);
     if with_header {