[9.x] Added callback support on implode Collection method. (#41405)

* [9.x] Added callback support on implode Collection method.

Allow to use a callback as `$value` on `implode` Collection method to simplify -`>map()->implode()` calls:

Before:

```php
<span>{{ $user->cities->map(fn ($city) => $city->name.' ('.$city->state->name.')')->implode(', ') }}</span>
```

After:

```php
<span>{{ $user->cities->implode(fn ($city) => $city->name.' ('.$city->state->name.')', ', ') }}</span>
```

* Added implode callback test

Collection.php

@@ -577,12 +577,16 @@ public function hasAny($key)
     /**
      * Concatenate values of a given key as a string.
      *
-     * @param  string  $value
+     * @param  callable|string  $value
      * @param  string|null  $glue
      * @return string
      */
     public function implode($value, $glue = null)
     {
+        if (is_callable($value)) {
+            return implode($glue ?? '', $this->map($value)->all());
+        }
+
         $first = $this->first();
 
         if (is_array($first) || (is_object($first) && ! $first instanceof Stringable)) {