PSR12/ClassInstantiation: fix regression for new parent

Related to 3546 which fixed an inconsistency after 3484.

The change of the tokenization from `T_STRING` to `T_PARENT` for the `parent` keyword in `new parent` caused a regression in the `PSR12.Classes.ClassInstantiation` sniff.

Fixed now.

Includes unit tests.

src/Standards/PSR12/Sniffs/Classes/ClassInstantiationSniff.php

@@ -50,6 +50,7 @@ public function process(File $phpcsFile, $stackPtr)
             T_NAME_RELATIVE            => T_NAME_RELATIVE,
             T_SELF                     => T_SELF,
             T_STATIC                   => T_STATIC,
+            T_PARENT                   => T_PARENT,
             T_VARIABLE                 => T_VARIABLE,
             T_DOLLAR                   => T_DOLLAR,
             T_OBJECT_OPERATOR          => T_OBJECT_OPERATOR,

src/Standards/PSR12/Tests/Classes/ClassInstantiationUnitTest.inc

@@ -42,3 +42,6 @@ $class = new ${$obj?->classname};
 $anonWithAttribute = new #[SomeAttribute('summary')] class {
     public const SOME_STUFF = 'foo';
 };
+
+$foo = new parent();
+$foo = new parent;

src/Standards/PSR12/Tests/Classes/ClassInstantiationUnitTest.inc.fixed

@@ -42,3 +42,6 @@ $class = new ${$obj?->classname}();
 $anonWithAttribute = new #[SomeAttribute('summary')] class {
     public const SOME_STUFF = 'foo';
 };
+
+$foo = new parent();
+$foo = new parent();

src/Standards/PSR12/Tests/Classes/ClassInstantiationUnitTest.php

@@ -43,6 +43,7 @@ public function getErrorList()
             34 => 1,
             37 => 1,
             38 => 1,
+            47 => 1,
         ];
 
     }//end getErrorList()