Improved implementation of Spark CVE-2022-33891 detector

[lokiuox]

The previous implementation was prone to false positives as, in absence of the Callback Server, it would resort to just measuring the time taken by the HTTP response.

The following modifications were done in accordance with the Tsunami team:

• The detector can now only run when the Callback Server is available. The time-measuring branch was removed.
• Implemented a small fingerprinting step
• Added a 5s delay before the callback server is polled to account for slow targets
• Fixed the tests accordingly