PHP 8.5 | Tests: prevent deprecation notice for Reflection*::setAccessible()

[jrfnl]

Since PHP 8.1, calling the Reflection*::setAccessible() methods is no longer necessary as reflected properties/methods/etc will always be accessible. However, the method calls are still needed for PHP < 8.1.

As of PHP 8.5, calling the Reflection*::setAccessible() methods is now formally deprecated and will yield a deprecation notice, which will fail test runs. As of PHP 9.0, the setAccessible() method(s) will be removed.

With the latter in mind, this commit prevents the deprecation notice by making the calls to setAccessible() conditional.

Silencing the deprecation would mean this would need to be "fixed" again come PHP 9.0, while the current solution should be stable, including for PHP 9.0.

Ref: https://wiki.php.net/rfc/deprecations_php_8_5#extreflection_deprecations

[jrfnl]

Note: I expect this won't fix all notices yet as we're also using TestUtils from PHPCSUtils. A PR to fix those is already open and a new release is expected soon.

[jrfnl]

Note: aside from the deprecation notices from PHPCSUtils, there is one actual test failure:

1) PHPCompatibility\Tests\TypeCasts\NewTypeCastsUnitTest::testNewTypeCasts with data set #1 ('The binary cast', '5.2.0', [9, 10, 11, 12, 16, 18], '5.3', '5.2')
Expected error 'The binary cast is not present in PHP version 5.2.0 or earlier' on line number 9, but none found.

This is due to a bug in the deprecation code in PHP Core itself. A fix for this has already been merged upstream and the build should pass again once the setup-php nightly image for PHP 8.5 has regenerated somewhere in the next 24 hours.