Remove NullToStrictStringIntConverter, use explicit null type in null-to-strict rules (#8837)

Author: TomasVotruba

rules-tests/Php81/Rector/FuncCall/NullToStrictStringFuncCallArgRector/Fixture/case_insensitive_function_name.php.inc

@@ -22,7 +22,7 @@ class NullDefinedInVariableFirst
     public function getTitle()
     {
         $title = null;
-        return trim((string) $title);
+        return trim('');
     }
 }
 

rules-tests/Php81/Rector/FuncCall/NullToStrictStringFuncCallArgRector/Fixture/crypt_one_arg.php.inc

@@ -0,0 +1,13 @@
+<?php
+
+namespace Rector\Tests\Php81\Rector\FuncCall\NullToStrictStringFuncCallArgRector\Fixture;
+
+final class CaseInsensitiveFunctionName
+{
+    public function run($var)
+    {
+        return strToLower($var);
+    }
+}
+
+?>

rules-tests/Php81/Rector/FuncCall/NullToStrictStringFuncCallArgRector/Fixture/explicit_mixed_in_trait.php.inc

@@ -0,0 +1,18 @@
+<?php
+
+namespace Rector\Tests\Php81\Rector\FuncCall\NullToStrictStringFuncCallArgRector\Fixture;
+
+/**
+ * Crypt requires 2 args since php 5.6, when it only fill 1st arg, it will only change 1st arg
+ *
+ * Note: Filling 2nd arg will require different Rule to match the salt algorithm.
+ */
+final class CryptOneArg
+{
+    public function run($subject)
+    {
+        crypt($subject);
+    }
+}
+
+?>