Fix incorrect Annotation::fetchAll() return structure for single Examples attribute

[xEdelweiss]

I had an issue similar to #6726, caused by how Annotation::fetchAll() handles the single #[Examples] attribute.

Here are comparison of fetchAll() return structures:

# Multiple Example attributes:
array (
  0 => array (
    0 => 'example 1',
  ),
  1 => array (
    0 => 'example 2',
  ),
)

# ❌ Single Example attribute (actual):
array (
  0 => 'example 1', 
)

# ✔️ Single Example attribute (expected):
array (
  0 => array (
    0 => 'example 1',
  ),
)

This PR includes a fix and unit-tests update for this issue. It also has a test for the #[Given] attribute to show that the changes do not break it.

[Naktibalda]

This change broke tests\cli\RunCest.php:runWithExamples

Please fix it.

[xEdelweiss]

I've missed this test, but it is the one that highlights the issue and conflicts with the changes I propose in this PR.

It is confusing that a single #[Example] attribute is treated not in the same way as multiple ones.
This also forces you to update attribute arguments when you move from single #[Example] to multiple and vice versa.

Like in this flow:

// write simple test - works

#[Examples([1, 1])]
public function example1(AttrsTester $I, Example $e)
{
    $I->assertEquals($e[1], $e[0]);
}

// duplicate line, update data - fails

#[Examples([1, 1])]
#[Examples([2, 2])]
public function example2(AttrsTester $I, Example $e)
{
    $I->assertEquals($e[1], $e[0]);
}

// unwrap arrays to make it work - works

#[Examples(1, 1)]
#[Examples(2, 2)]
public function example3(AttrsTester $I, Example $e)
{
    $I->assertEquals($e[1], $e[0]);
}

// same in the opposite direction

I see how this change can introduce backward incompatibility for those who have used a single #[Example]. But since the documentation does not describe the specific behavior of a single #[Example], I don't think it's a big issue compared to the improved developer experience.

So I propose to update the tests\cli\RunCest.php:runWithExamples.

I'd appreciate your thoughts on this.

[Naktibalda]

phpcs doesn't like style of this file

[xEdelweiss]

Sorry, my bad. Missed PHPCS checks. Fixed.