[5.8] Allow console environment argument to be separated with a space

[ThibaudDauce]

Following explanations are from @matt-allan in the issue #28831:

The Symfony console component that is used by the Artisan console allows separating option names and values with either a space or an equals (=) sign. For example:

$ php artisan serve --port=9090 
Laravel development server started: <http://127.0.0.1:9090>
$ php artisan serve --port 9090 
Laravel development server started: <http://127.0.0.1:9090>

However, the --env option is only parsed correctly if you use an equals sign. If you use a space app()->environment() will return false.

This inconsistency is pretty confusing and difficult to debug. If you dump $this->option('env') in a command it will return the expected value but app()->environment() will return false.

Fixes #28831