refactor(core): decouple discovery

[brendt]

A couple of changes with this PR:

• Adding the Registry class, which keeps track of loaded discovery locations and classes. For now there's a passthrouh in FrameworkKernel to ensure backwards compatibility. Thanks to this class though, there are less dependencies between discovery and core
• Also moving the Composer class from core to discovery, totally eliminating all dependencies between the two. Everything that uses Composer also uses Discovery, so I think it's fine to keep it there for now (I want to avoid making another package just for the sake of it with one class)
• Then… what I so long resisted doing. GenericContainer now implements Psr\Container\ContainerInterface. Luckily PHP's variance checker is smart enough to allow our implementation, and it's actually compatible out of the box.
• Finally, discovery now uses the PSR container. I first made the container fully optional, but I don't see how that's useful: you need to do something with discovered items, and I think it makes sense that all of that goes through a container of some sorts.

Here are two examples of how discovery can be used standalone. First you require tempest/discovery, nothing else.

Then, you can for example do this:

// Registry setup, `tempest/framework` does this for you, but as a standalone package you must manage it yourself.
// Probably worth improving in the future.
$registry = new Registry(locations: [
    new DiscoveryLocation('Tempest\\Discovery\\', __DIR__ . '/vendor/tempest/discovery/src/'),
    new DiscoveryLocation('App\\', __DIR__ . '/src'),
]);

// A dummy container setup, I assume a real project already has it set up. What's important is that both the registry and container itself are available in the container.
$container = new Tempest\Container\GenericContainer();
$container->singleton(Registry::class, $registry);
$container->singleton(Container::class, $container);

// This is the actual discovery code. By default, `DiscoveryConfig` will use symfony's file adapter, but people can adjust however they like. I'm going to improve this even more.
$loadDiscovery = new LoadDiscoveryClasses(
    registry: $registry,
    discoveryConfig: new DiscoveryConfig(),
    discoveryCache: new DiscoveryCache(DiscoveryCacheStrategy::NONE),
    container: $container,
);

$loadDiscovery();

Then here's an example with the php-di container:

$builder = new ContainerBuilder();
$container = $builder->build();
$container->set(Registry::class, $registry);
$container->set(Container::class, $container);
$container->set(AppDiscovery::class, new AppDiscovery($container));

$loadDiscovery = new LoadDiscoveryClasses(
    registry: $registry,
    discoveryConfig: new DiscoveryConfig(),
    discoveryCache: new DiscoveryCache(DiscoveryCacheStrategy::NONE),
    container: $container,
);

$loadDiscovery();

[github-actions]

Benchmark Results

Comparison of discovery-improvements against 3.x (ab8cfb14398f19936e9c4be649a2c42c805dbcf1).

Open to see the benchmark results

Benchmark	Set	Mem. Peak	Time	Variability
ViewRenderBench(benchExpressions)	-	23.974mb +0.01%	553.138μs +7.09%	±1.60% -51.61%

_{Generated by phpbench against commit f616bdc}

[iamdadmin]

Aidan's not the only one who loves the commits :D