[DeadCode] Add RemoveDeadInstanceOfAssertRector

[TomasVotruba]

Adds a new dead-code rule that removes redundant assert($value instanceof X) statements when the value's type is already known to be X (or a subtype).

Covers property fetches and variables.

 final class SomeClass
 {
     public function __construct(
         private UserRepository $userRepository
     ) {
     }

     public function run(): void
     {
-        assert($this->userRepository instanceof UserRepository);
     }
 }

Kept (not changed):

// nullable property - instanceof is not always true
assert($this->userRepository instanceof UserRepository); // ?UserRepository

// untyped property - type unknown
assert($this->userRepository instanceof UserRepository); // private $userRepository

// carries a description message - preserved
assert($this->userRepository instanceof UserRepository, 'must be set');

Registered in DeadCodeLevel.