vim: Update change surrounds to match vim's behavior (#38721)

These changes refactor the whitespace handling logic for Vim's change
surrounds command (`cs`), making its behavior closely match
[tpope/vim-surround](https://github.com/tpope/vim-surround), following
[this
discussion](https://github.com/zed-industries/zed/issues/38169#issuecomment-3304129461).

Zed's current implementation has two main differences when compared to
[tpope/vim-surround](https://github.com/tpope/vim-surround):

- It only considers whether a single space should be added or removed,
instead of all the space that is between the surrounding character and
the content
- It only takes into consideration the new surrounding characters in
order to determine whether to add or remove that space

A review of
[tpope/vim-surround](https://github.com/tpope/vim-surround)'s behavior
reveals these rules for whitespace:

* Quote to Quote
    * Whitespace is never changed
* Quote to Bracket
    * If opening bracket, add one space
    * If closing bracket, do not add space
* Bracket to Bracket
    * If opening to opening, keep only one space
    * If opening to closing, remove all space
    * If closing to opening, add one space
    * If closing to closing, do not change space
* Bracket to Quote
    * If opening, remove all space
    * If closing, preserve all space

Below is a table with examples for each scenario. A new test has also
been added to specifically check the scenarios outlined above,
`vim::surrounds::test::test_change_surrounds_vim`.

| Type              | Before      | Command | After         |
|-------------------|-------------|---------|---------------|
| Quote → Quote     | `'   a   '` | `cs'"`  | `"   a   "`   |
| Quote → Quote     | `"   a   "` | `cs"'`  | `'   a   '`   |
| Quote → Bracket   | `'   a   '` | `cs'{`  | `{    a    }` |
| Quote → Bracket   | `'   a   '` | `cs'}`  | `{   a   }`   |
| Bracket → Bracket | `[   a   ]` | `cs[{`  | `{ a }`       |
| Bracket → Bracket | `[   a   ]` | `cs[}`  | `{a}`         |
| Bracket → Bracket | `[   a   ]` | `cs]{`  | `{    a    }` |
| Bracket → Bracket | `[   a   ]` | `cs]}`  | `{   a   }`   |
| Bracket → Quote   | `[   a   ]` | `cs['`  | `'a'`         |
| Bracket → Quote   | `[   a   ]` | `cs]'`  | `'   a   '`   |

These changes diverge from
[tpope/vim-surround](https://github.com/tpope/vim-surround) when
handling newlines. For example, with the following snippet:

```rust
fn test_surround() {
    if 2 > 1 {
        println!("place cursor here");
    }
};
```

Placing the cursor inside the string and running any combination of
‎`cs{[`, ‎`cs{]`, ‎`cs}[`, or ‎`cs}]` would previously remove newline
characters. With these changes, using commands like ‎`cs}]` will now
preserve newlines.

Related to #38169
Closes #39334

Release Notes:

- Improved Vim’s change surround command to closely match
[tpope/vim-surround](https://github.com/tpope/vim-surround) behavior.

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/vim/src/normal.rs

@@ -450,6 +450,7 @@ impl Vim {
         &mut self,
         object: Object,
         times: Option<usize>,
+        opening: bool,
         window: &mut Window,
         cx: &mut Context<Self>,
     ) {
@@ -520,10 +521,11 @@ impl Vim {
             Some(Operator::DeleteSurrounds) => {
                 waiting_operator = Some(Operator::DeleteSurrounds);
             }
-            Some(Operator::ChangeSurrounds { target: None }) => {
+            Some(Operator::ChangeSurrounds { target: None, .. }) => {
                 if self.check_and_move_to_valid_bracket_pair(object, window, cx) {
                     waiting_operator = Some(Operator::ChangeSurrounds {
                         target: Some(object),
+                        opening,
                     });
                 }
             }