Fix Autoloader::initialize()

[kenjis]

Description

• reset the state when initialize() is called

$ ./phpunit --exclude-group DatabaseLive,CacheLive 

Memory: 188.00 MB <- before
Memory: 186.00 MB <- after

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• [] User guide updated
• Conforms to style guide

[MGatner]

I'm not actually sure what all the implications of this are but it seems like the right thing to do. Tests all look good.

[kenjis]

@MGatner Without this PR, the paths are added again and again in testing.

        $loader = new Autoloader();
        $loader->initialize(new Autoload(), new Modules());
        $loader->initialize(new Autoload(), new Modules());
        dd($loader->getNamespace());

array (45) [
    'CodeIgniter' => array (2) [
        0 => string (50) "/Users/kenji/work/codeigniter/CodeIgniter4/system/"
        1 => string (50) "/Users/kenji/work/codeigniter/CodeIgniter4/system/"
    ]
    'App' => array (2) [
        0 => string (47) "/Users/kenji/work/codeigniter/CodeIgniter4/app/"
        1 => string (47) "/Users/kenji/work/codeigniter/CodeIgniter4/app/"
    ]
...