Best-effort run metadata uploads capped at 15 seconds

Best-effort run metadata uploads are now bounded by a 15-second timeout, both when they run in the foreground on CI and when they run in the hidden background process used by local commands. Commands such as tuist install no longer block for several minutes on Uploading run metadata... when the configured server is slow or unhealthy, and the hidden background upload no longer lingers on a bad connection. Required report-producing analytics keep their previous behavior, and the bound also stops retry-wrapped server calls promptly on cancellation.