Support Direct dem file upload for S3 object storage

[FlowingSPDG]

Hello! It's been a while since I was so away from CS2 for long time!

I had a automated tournament system with G5API, but we had difficulties with uploading dem files since dem file easily exceeds 150Mb which hits most storage service's limit.

If i could upload dem file to S3 directly, it is going be awesome for tournament mangers and league runners.

I am thinking to add these changes if that's okay for both of us:

1. Add CVAR e.g. matchzy_demo_upload_s3

[ConsoleCommand("matchzy_demo_upload_s3", "Whether upload demo to S3 is enabled or not. Default value: false")]
public void MatchZyDemoUploadS3Convar(CCSPlayerController? player, CommandInfo command)
{
     if (player != null) return;
     string args = command.ArgString;
     isDemoUploadS3Enabled = bool.TryParse(args, out bool isDemoUploadS3EnabledValue) ? isDemoUploadS3EnabledValue : args != "0" && isDemoUploadS3Enabled;
}

2. Once Server finished recording demo, check matchzy_demo_upload_s3
3. Upload for pre-signed URL with S3-compatible HTTP request(PUT)