PSR12/Squiz/OperatorSpacing: bug fix with arrow functions

The plus/minus in a default value of a function parameter declaration is ignored for normal functions and closures, but wasn't ignored yet for arrow functions.

Fixed now.

Includes unit test + test for the same for closures, which so far wasn't tested yet.

This also, by extension, fixes the same issue in the `PSR12.Operators.OperatorSpacing` sniff.

src/Standards/Squiz/Sniffs/WhiteSpace/OperatorSpacingSniff.php

@@ -344,6 +344,7 @@ protected function isOperator(File $phpcsFile, $stackPtr)
                     $function = $tokens[$bracket]['parenthesis_owner'];
                     if ($tokens[$function]['code'] === T_FUNCTION
                         || $tokens[$function]['code'] === T_CLOSURE
+                        || $tokens[$function]['code'] === T_FN
                         || $tokens[$function]['code'] === T_DECLARE
                     ) {
                         return false;

src/Standards/Squiz/Tests/WhiteSpace/OperatorSpacingUnitTest.inc

@@ -463,5 +463,10 @@ $a = [$a, - $b];
 $a = $a[- $b];
 $a = $a ? - $b : - $b;
 
+$cl = function ($boo =-1) {};
+$cl = function ($boo =+1) {};
+$fn = fn ($boo =-1) => $boo;
+$fn = fn ($boo =+1) => $boo;
+
 /* Intentional parse error. This has to be the last test in the file. */
 $a = 10 +

src/Standards/Squiz/Tests/WhiteSpace/OperatorSpacingUnitTest.inc.fixed

@@ -457,5 +457,10 @@ $a = [$a, - $b];
 $a = $a[- $b];
 $a = $a ? - $b : - $b;
 
+$cl = function ($boo =-1) {};
+$cl = function ($boo =+1) {};
+$fn = fn ($boo =-1) => $boo;
+$fn = fn ($boo =+1) => $boo;
+
 /* Intentional parse error. This has to be the last test in the file. */
 $a = 10 +