fix(toml_edit): reformat dotted keyed-items in TableLike::fmt

`TableLike::fmt` only reset the decor of value items, leaving dotted
keyed-items untouched. They are stored as dotted tables and dotted
inline tables, so recurse into them to reformat their key segments and
nested values as well.

Fixes #262

crates/toml_edit/tests/testsuite/edit.rs

@@ -1238,6 +1238,44 @@ fn test_format_array() {
     "#]]);
 }
 
+#[test]
+fn test_format_dotted_keys() {
+    given(
+        r#"
+        a . b  =  1
+        c  =  2
+        d . e . f  =  3
+        "#,
+    )
+    .running(|root| {
+        root.fmt();
+    })
+    .produces_display(str![[r#"
+a.b = 1
+c = 2
+d.e.f = 3
+        
+"#]]);
+}
+
+#[test]
+fn test_format_dotted_keys_in_inline_table() {
+    given(
+        r#"
+        a = { b . c  =  1, d  =  2 }
+        "#,
+    )
+    .running(|root| {
+        let a = root.get_mut("a").unwrap().as_inline_table_mut().unwrap();
+        a.fmt();
+    })
+    .produces_display(str![[r#"
+
+        a = { b.c = 1, d = 2 }
+        
+"#]]);
+}
+
 macro_rules! as_inline_table {
     ($entry:ident) => {{
         assert!($entry.is_value());