[DeadCode] Add RemoveDefaultValueFromAssignedPropertyRector

[TomasVotruba]

Fixes rectorphp/rector#9822

A property with a redundant default value is never given readonly by ReadOnlyPropertyRector, because the default value blocks it. The default is dead: the property is always overwritten in the constructor.

This rule removes that redundant default from typed properties that are unconditionally assigned in the constructor, so downstream rules (like ReadOnlyPropertyRector) start working as expected.

 final class SomeClass
 {
-    private ?SomeType $someType = null;
+    private ?SomeType $someType;

     public function __construct(SomeType $someType)
     {
         $this->someType = $someType;
     }
 }

Any default is dead, not only = null:

 final class SomeClass
 {
-    private int $value = 5;
+    private int $value;

     public function __construct(int $value)
     {
         $this->value = $value;
     }
 }

Scope / guards:

• Only typed properties. Untyped = null is already handled by RemoveNullPropertyInitializationRector.
• Only when the property is unconditionally assigned in the constructor (conditional assignment is skipped, so an uninitialized-access error can't be introduced).
• Properties with hooks are skipped.