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/state.rs

@@ -109,6 +109,9 @@ pub enum Operator {
     },
     ChangeSurrounds {
         target: Option<Object>,
+        /// Represents whether the opening bracket was used for the target
+        /// object.
+        opening: bool,
     },
     DeleteSurrounds,
     Mark,
@@ -1077,7 +1080,9 @@ impl Operator {
             | Operator::Replace
             | Operator::Digraph { .. }
             | Operator::Literal { .. }
-            | Operator::ChangeSurrounds { target: Some(_) }
+            | Operator::ChangeSurrounds {
+                target: Some(_), ..
+            }
             | Operator::DeleteSurrounds => true,
             Operator::Change
             | Operator::Delete
@@ -1094,7 +1099,7 @@ impl Operator {
             | Operator::ReplaceWithRegister
             | Operator::Exchange
             | Operator::Object { .. }
-            | Operator::ChangeSurrounds { target: None }
+            | Operator::ChangeSurrounds { target: None, .. }
             | Operator::OppositeCase
             | Operator::ToggleComments
             | Operator::HelixMatch
@@ -1121,7 +1126,7 @@ impl Operator {
             | Operator::Rewrap
             | Operator::ShellCommand
             | Operator::AddSurrounds { target: None }
-            | Operator::ChangeSurrounds { target: None }
+            | Operator::ChangeSurrounds { target: None, .. }
             | Operator::DeleteSurrounds
             | Operator::Exchange
             | Operator::HelixNext { .. }