Expose Container API to allow explicit DI container configuration

[clue]

This changeset exposes the Container API to allow explicit DI container configuration. This allows us to fine-tune the autowiring behavior and explicitly overwrite autowiring defaults for more advanced use cases. This does not otherwise break existing APIs, so this is a pure feature addition.

<?php

require __DIR__ . '/../vendor/autoload.php';

$container = new FrameworkX\Container([
    Acme\Todo\HelloController::class => fn() => new Acme\Todo\HelloController();
]);

$app = new FrameworkX\App($container);

$app->get('/', Acme\Todo\HelloController::class);
$app->get('/users/{name}', Acme\Todo\UserController::class);

$app->run();

PSR-11 compatibility is on the roadmap, but left up for a follow-up PR.

Builds on top of #94 and #92