Squiz/FunctionDeclarationArgumentSpacing: improve SpacingAfterVariadic fixer

The fixer for the `SpacingAfterVariadic` error code would only handle one whitespace token at a time, which is inefficient and could also lead to more complex fixer conflicts.

This commit changes the fixer to handle all whitespace tokens after a variadic token in one go.

For the test code sample added in the previous commit, this means the difference between the fixer needing 5 loops (including one skipped loop due to possible conflicts) versus 2 loops.

<details>
  <summary>Old:</summary>

```
        => Fixing file: 1/1 violations remaining
        Squiz.Functions.FunctionDeclarationArgumentSpacing:190 replaced token 9 (T_WHITESPACE on line 4) "\n\n" => "\n"
        => Fixing file: 1/1 violations remaining [made 1 pass]...
        * fixed 1 violations, starting loop 2 *
        Squiz.Functions.FunctionDeclarationArgumentSpacing:190 replaced token 9 (T_WHITESPACE on line 4) "\n    " => "    "
        => Fixing file: 1/1 violations remaining [made 2 passes]...
        * fixed 1 violations, starting loop 3 *
        **** Squiz.Functions.FunctionDeclarationArgumentSpacing:190 has possible conflict with another sniff on loop 1; caused by the following change ****
        **** replaced token 9 (T_WHITESPACE on line 4) "    $param" => "$param" ****
        **** ignoring all changes until next loop ****
        => Fixing file: 0/1 violations remaining [made 3 passes]...
        * fixed 0 violations, starting loop 4 *
        Squiz.Functions.FunctionDeclarationArgumentSpacing:190 replaced token 9 (T_WHITESPACE on line 4) "    $param" => "$param"
        => Fixing file: 1/1 violations remaining [made 4 passes]...
        * fixed 1 violations, starting loop 5 *
        => Fixing file: 0/1 violations remaining [made 5 passes]...
```
</details>

<details>
  <summary>New:</summary>

```
        => Fixing file: 1/1 violations remaining
        => Changeset started by Squiz.Functions.FunctionDeclarationArgumentSpacing:190
                Q: Squiz.Functions.FunctionDeclarationArgumentSpacing:192 replaced token 9 (T_WHITESPACE on line 4) "\n\n" => "\n"
                Q: Squiz.Functions.FunctionDeclarationArgumentSpacing:192 replaced token 10 (T_WHITESPACE on line 5) "\n    " => "    "
                Q: Squiz.Functions.FunctionDeclarationArgumentSpacing:192 replaced token 11 (T_WHITESPACE on line 6) "    $param" => "$param"
                A: Squiz.Functions.FunctionDeclarationArgumentSpacing:195 replaced token 9 (T_WHITESPACE on line 4) "\n\n" => "\n"
                A: Squiz.Functions.FunctionDeclarationArgumentSpacing:195 replaced token 10 (T_WHITESPACE on line 5) "\n    " => "    "
                A: Squiz.Functions.FunctionDeclarationArgumentSpacing:195 replaced token 11 (T_WHITESPACE on line 6) "    $param" => "$param"
        => Changeset ended: 3 changes applied
        => Fixing file: 3/1 violations remaining [made 1 pass]...
        * fixed 3 violations, starting loop 2 *
        => Fixing file: 0/1 violations remaining [made 2 passes]...
```
</details>

Author: jrfnl

src/Standards/Squiz/Sniffs/Functions/FunctionDeclarationArgumentSpacingSniff.php

@@ -188,9 +188,14 @@ public function processBracket($phpcsFile, $openBracket)
                     ];
                     $fix   = $phpcsFile->addFixableError($error, $variadicToken, 'SpacingAfterVariadic', $data);
                     if ($fix === true) {
-                        $phpcsFile->fixer->replaceToken(($variadicToken + 1), '');
+                        $phpcsFile->fixer->beginChangeset();
+                        for ($i = ($variadicToken + 1); $tokens[$i]['code'] === T_WHITESPACE; $i++) {
+                            $phpcsFile->fixer->replaceToken($i, '');
+                        }
+
+                        $phpcsFile->fixer->endChangeset();
                     }
-                }
+                }//end if
             }//end if
 
             if (isset($param['default_equal_token']) === true) {