Allow magic methods __serialize and __unserialize in CamelCapsFunctionNameSniff

[ludekbenedik]

Describe the bug
The sniff Generic.NamingConventions.CamelCapsFunctionName.MethodDoubleUnderscore does not known magic methods __serialize and __unserialize.

Code sample

<?php declare(strict_types = 1);

namespace App;

class Test
{
    public function __serialize(): array
    {
        return [];
    }

    public function __unserialize(array $data): void
    {
    }
}

To reproduce

  7 | ERROR | Method name "Test::__serialize" is invalid; only PHP
    |       | magic methods should be prefixed with a double
    |       | underscore
    |       | (Generic.NamingConventions.CamelCapsFunctionName.MethodDoubleUnderscore)
 12 | ERROR | Method name "Test::__unserialize" is invalid; only PHP
    |       | magic methods should be prefixed with a double
    |       | underscore
    |       | (Generic.NamingConventions.CamelCapsFunctionName.MethodDoubleUnderscore)

Expected behavior
None error

Versions (please complete the following information):

• OS: [*]
• PHP: [7.4]
• PHPCS: [3.5.5 (stable)]
• Standard: [Generic]