[9.x] Make sure the prefix override behaviours are the same between phpredis and predis drivers

[s-patompong]

Yesterday I was doing research for the company (mainly to do with Redis prefix options) and I found that there are two problems with the implementation of the \Illuminate\Redis\Connectors\PhpRedisConnector::connect method.

The first issue is that we use Arr::pull to pull the options from the config array, like so:

$connector = function () use ($config, $options, $formattedOptions) {
    return $this->createClient(array_merge(
        $config, $options, Arr::pull($config, 'options', [])
    ));
};

The issue with this code is that the Arr::pull won't take effect and the final array from the array_merge will contain the options key, as I can show you here in a simple dd snippet:

$config = [
    'host' => 'redis.com',
    'options' => [
        'prefix' => 'config_redis_',
    ],
];

$options = [
    'prefix' => 'redis_'
];

dd(array_merge($config, $options, Arr::pull($config, 'options', [])));

The output is

[
  "host" => "redis.com"
  "options" => array:1 [
    "prefix" => "config_redis_"
  ]
  "prefix" => "config_redis_"
]

This PR will make sure that we pull out the options key from the config so that we don't merge it into the final array. This is merely just a DX touch.

Secondly, I found that in the \Illuminate\Redis\Connectors\PredisConnector::connect method, we have the code to override the prefix inside the options key of each redis config with the config's prefix key itself.

This means for predis driver, the prefix for this config will be config_:

[
    'scheme' => 'tcp',
    'host' => $host,
    'port' => $port,
    'database' => 5,
    'timeout' => 0.5,
    'options' => [
        'prefix' => 'config_options_',
    ],
    'prefix' => 'config_',
]

However, if you use phpredis driver, the prefix that will be used in the connector is config_options_.

This PR makes sure that the prefix override behaviour of the phpredis is working in the same way with the predis connector. This means such config would resolves in the prefix = config_.