fix: support higher-order method calls on expectations

[imKenjo18]

Fixes pestphp/pest#1896

Problem

When chaining method calls directly on an expectation:

$policy = new UserPolicy;

expect($policy)
    ->view($user1, $user1)->toBeTrue()
    ->update($user1, $user1)->toBeTrue()
    ->view($user1, $user2)->toBeFalse();

It causes two PHPStan errors:

• Call to an undefined method Pest\Expectation<UserPolicy>::view()
• Calling toBeTrue() on Expectation<UserPolicy>; assertion is impossible.

Solution

• Added reflection support for dynamic methods on Expectation and HigherOrderExpectation.
• Inferred the method return type (supporting arguments, enums, and nested property chains) and wrapped it in HigherOrderExpectation.
• Passed the method return type down the expectation chain so rules like ImpossibleExpectationRule evaluate against the returned value rather than the parent object.