Added code required to handle Traversable objects

[Viliasas]

When using apcu-simple-cache with latest version of PhpSpreadsheet (https://github.com/PHPOffice/PhpSpreadsheet) we're getting this error:

Fatal error: Uncaught TypeError: Argument 1 passed to Paillechat\ApcuSimpleCache\ApcuCache::assertKeyNames() must be of the type array, object given, called in /var/www/orders/vendor/paillechat/apcu-simple-cache/src/ApcuCache.php on line 124 and defined in /var/www/orders/vendor/paillechat/apcu-simple-cache/src/ApcuCache.php:183 Stack trace: #0 /var/www/orders/vendor/paillechat/apcu-simple-cache/src/ApcuCache.php(124): Paillechat\ApcuSimpleCache\ApcuCache->assertKeyNames(Object(Generator)) #1 /var/www/orders/vendor/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Collection/Cells.php(492): Paillechat\ApcuSimpleCache\ApcuCache->deleteMultiple(Object(Generator)) #2 /var/www/orders/vendor/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Collection/Cells.php(479): PhpOffice\PhpSpreadsheet\Collection\Cells->__destruct() #3 /var/www/orders/vendor/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Worksheet/Worksheet.php(385): PhpOffice\PhpSpreadsheet\Collection\Cells->unsetWorksheetCells() #4 /var/www/orders/vendor/phpoffice/phpspreadsheet/src/ in /var/www/orders/vendor/paillechat/apcu-simple-cache/src/ApcuCache.php on line 183

It seems that apcu-simple-cache does not work with Traversable objects as defined in PSR-16 (https://www.php-fig.org/psr/psr-16/).

To solve this I've added few checks for object and in the end decided to convert Traversable objects to arrays. I've done this so, because Generators can be traversed only once.

[paillechat]

Hello, can we just change the signature of assertKeyNames, I think we can replace array to iterable and it helps, is it?

[Viliasas]

Hi, it's not enough to remove signatures from assertKeyNames and buildKeyNames functions, because they use array_map function. It requires second parameter to be an array (http://docs.php.net/manual/da/function.array-map.php).

[paillechat]

Ok, can you write a test for that case?