Don't require parentheses for short-ternaries (#7604)

Chaining of short-ternaries (`?:` also called elvis operator) is stable
and behaves reasonably

This is described in the PHP Manual right below the warning about using
nested ternary expressions.

The example code is taken from the PHP Manual.

https://www.php.net/manual/en/language.operators.comparison.php#:~:text=Chaining%20of%20short%2Dternaries%20(%3F%3A)%2C%20however%2C%20is%20stable%20and%20behaves%20reasonably

Author: martinstuecklschwaiger

rules-tests/Php74/Rector/Ternary/ParenthesizeNestedTernaryRector/Fixture/skip_elvis.php.inc

@@ -0,0 +1,8 @@
+<?php
+
+function elvisDoesNotNeedParentheses()
+{
+  echo 0 ?: 1 ?: 2 ?: 3, PHP_EOL; //1
+  echo 0 ?: 0 ?: 2 ?: 3, PHP_EOL; //2
+  echo 0 ?: 0 ?: 0 ?: 3, PHP_EOL; //3
+}

rules/Php74/Rector/Ternary/ParenthesizeNestedTernaryRector.php

@@ -61,6 +61,12 @@ public function getNodeTypes(): array
     public function refactor(Node $node): ?Node
     {
         if ($node->cond instanceof Ternary || $node->else instanceof Ternary) {
+            // Chaining of short-ternaries (elvis operator) is stable and behaves reasonably
+            $isElvis = $node->cond instanceof Ternary && $node->cond->if === null;
+            if ($isElvis) {
+                return null;
+            }
+
             if ($this->parenthesizedNestedTernaryAnalyzer->isParenthesized($this->file, $node)) {
                 return null;
             }