[CodeQuality] Flip void-method with(callback) to willReturnCallback, rename rule

[TomasVotruba]

Renames RemoveReturnFromVoidMethodMockCallbackRector → VoidMethodWithCallbackToWillReturnCallbackRector and refocuses it.

The old name no longer described the behavior: the rule now flips a ->with($this->callback(...)) matcher on a void mocked method into a ->willReturnCallback() call, dropping the now-pointless value return and typing the closure as void. Plain ->willReturnCallback() closures are left untouched.

Before / after

 $this->createMock(SomeClass::class)
     ->method('run') // run(): void
-    ->with($this->callback(function ($arg) {
+    ->willReturnCallback(function ($arg): void {
         echo $arg;
-
-        return true;
-    }));
+    });

Notes

• Only applies when the mocked method returns void (reflection-checked).
• Safety kept: bails on nested closures and on non-pure returned values; return throw unwraps to a bare throw.
• Plain ->willReturnCallback(...) closures are left untouched.