Flysystem 3 support

[rskuipers]

As promised here is a PR with all the changes needed to support Flysystem 3.
We're currently using this in production and it works well.

I haven't touched any of the documentation yet so this is most definitely out-of-date.

We are currently running this with Redis as persistent cache:

---
Only:
  envvarset: REDIS_HOST
After:
  - 'silverstripegooglecloudstorage-flysystem'
  - '#corecache'
---
SilverStripe\Core\Injector\Injector:
  RedisClient:
    factory: App\Caching\RedisClientFactory
    constructor:
      host: '`REDIS_HOST`'
      port: '`REDIS_PORT`'
      db: '`REDIS_DB`'
      auth: '`REDIS_AUTH`'

  RedisCacheFactory:
    class: App\Caching\RedisCacheFactory
    constructor:
      client: '%$RedisClient'

  Symfony\Component\Cache\Adapter\FilesystemAdapter.protected:
    factory: '%$RedisCacheFactory'
    constructor:
      key: 'gcmetadata-protected'
      expire: 259200

  Symfony\Component\Cache\Adapter\FilesystemAdapter.public:
    factory: '%$RedisCacheFactory'
    constructor:
      key: 'gcmetadata-public'
      expire: 259200

The RedisCacheFactory looks like this:

<?php

declare(strict_types=1);

namespace App\Caching;

use Psr\Container\NotFoundExceptionInterface;
use Redis;
use SilverStripe\Core\Injector\Factory;
use SilverStripe\Core\Injector\Injector;
use Symfony\Component\Cache\Adapter\AdapterInterface;
use Symfony\Component\Cache\Adapter\ArrayAdapter;
use Symfony\Component\Cache\Adapter\ChainAdapter;
use Symfony\Component\Cache\Adapter\RedisAdapter;

class RedisCacheFactory implements Factory
{
    public function __construct(private readonly Redis $redis)
    {
    }

    /**
     * @param $service
     * @param array<string, mixed> $params
     * @return AdapterInterface
     * @throws NotFoundExceptionInterface
     */
    public function create($service, array $params = [])
    {
        $key = $params['key'];
        $expire = (int)$params['expire'];

        return new ChainAdapter([
            new ArrayAdapter(),
            Injector::inst()
                ->createWithArgs(
                    RedisAdapter::class,
                    [
                        $this->redis,
                        $key,
                        $expire,
                    ]
                ),
        ]);
    }
}

Here you can see we use the ChainAdapter to also do in-memory caching for even more speeeeeed.

Let me know what you think.

I also noticed another branch were similar changes were done for Flysystem 3 support, I probably should have opened a draft PR to make our efforts more visible to prevent doing twice the work. We had a project to launch so that's what I focused on :)