[2.x] Replace md5 with xxhash

[RobertBoes]

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Another attempt of #652

I recently noticed laravel/framework#52301, where most of the md5 calls will be replaced with xxhash, which is much faster than md5. For Inertia's asset versioning we don't need it to be cryptographically correct, but a performance improvement would be nice, especially since the middleware is executed on every request.

I think it's save to change this in the Inertia adapter, since all it would do is force a reload, which would happen when updating assets anyway.

Support for xxhash was added to PHP 8.1 (https://php.watch/versions/8.1/xxHash), so we can safely use this algorithm instead of md5.