Multiplayer Improvement: Upload files in parallel to minimize latency

[touhidurrr]

Ok
I added a 'copy stacktrace to clipboard' so in future errors it will be easier to debug

Also, this reminds me of something. I remember that game did not try to upload preview files when the main save file upload failed. Why are we not trying to upload these files in parallel. This should reduce next turn time in multiplayer.

Originally posted by @touhidurrr in #12997

Issue opened as to server as a reference to the discussion.

[yairm210]

Turns out there's a comment describing why!

    // We upload the preview after the game because otherwise the following race condition will happen:
    // Current player ends turn -> Uploads Game Preview
    // Other player checks for updates -> Downloads Game Preview
    // Current player starts game upload
    // Other player sees update in preview -> Downloads game, gets old state
    // Current player finishes uploading game

So we basically have to upload the preview AFTER the game

[touhidurrr]

I thought about this. But is that really an issue? If preview > main then the game simply reloads the main save file. Which resets the turn. So, i do not think we should honor this rare race condition.

[yairm210]

On the other hand, uploading the preview is so fast that it doesn't really save us any considerable time if we parallelize it

[touhidurrr]

Recently many are reporting high latency issues. If latency is even 300ms, the 2 files would take 600ms. 600 vs 300 looks like a good enough improvement for me.

[yairm210]

File upload time is usually based on size of file, the preview is a really tiny file
But you know what, we can test this and see, if we get people reporting weird MP errors we can revert it