[8.x] Support username parameter for predis

[SPie]

As mentioned in Issue #36298 the username parameter got filtered on creating parameters for the predis connection.
I removed the filter to enable the username parameter for the connection.

[taylorotwell]

So - surely we were filtering this for a reason? 🤔

[taylorotwell]

Does this cause problems with using the PHP Redis extension?

[SPie]

Does this cause problems with using the PHP Redis extension?

I couldn't see any problems with the PHP Redis extension because the username is not used for it. It just won't work right now because Illuminate\Redis\Connectors\PhpRedisConnector uses only the password parameter. To use the PHP Redis extension with username and password requires to have an array as password parameter:

'session' => [
            'password' => [env('REDIS_USERNAME'), env('REDIS_PASSWORD')],
],

[jitendra-1217]

Filed request to port the exact change into 6.x as well- #36762. Hoping it gets accepted.