Add async mechanism for time-based blind SQLi

[Saudadeeee]

Implements experimental asynchronous bisection for time-based blind SQL injection using aiohttp. Adds CLI options (--async, --async-time-based) to dramatically improve extraction speed by running binary search requests concurrently, while gracefully falling back to synchronous execution if dependencies are missing

[stamparm]

Thank you for the effort, but sqlmap already natively supports concurrent time-based extraction via the --threads flag, which intentionally prompts a warning because parallelizing time delays inherently causes database starvation and false positives. We will not introduce a bloated third-party dependency like aiohttp to completely bypass our core request engine and reinvent a fundamentally unstable wheel.

you are even presented with a prompt when using --threads and time-based SQLI:

multi-threading is considered unsafe in time-based data retrieval. Are you sure of your choice (breaking warranty) [y/N]

This architectural decision is final; we consider this matter closed and will not entertain further debates or pull requests attempting to force concurrent network I/O on time-based payloads.