Partial report contents leakage - via HTTP/2 concurrent stream handling

The concurrent handling of HTTP/2 streams allows for a "timeless timing attack": instead of timing, the ordering of responses is used, making the attack resilient to network jitter. As the `/bugs.json` endpoint takes slightly longer to process when a query returns results, it is possible to …

{
    "numCorrectBaseline": [11, 10, 9, 8, 6, 9, 10, 6, 10, 11],
    "numCorrectTarget": [15, 18, 14, 16, 15, 16, 14, 13, 16, 20]
}