Fix hanging issue in autotune timeout mechanism

[ChrisRackauckas-Claude]

Problem

The autotune feature would hang indefinitely when trying to timeout slow algorithms. This was caused by the timeout implementation attempting to forcefully interrupt tasks using Base.throwto(), which doesn't reliably work with tasks that are in certain states (like sleeping or blocked I/O).

Solution

Replace the problematic timeout mechanism with a more robust approach:

• Use Julia's built-in timedwait() function instead of manual polling
• Avoid using Base.throwto() which can cause hangs
• Let timed-out tasks continue running in the background rather than trying to forcefully kill them
• Use Channels for clean communication between tasks
• Properly close channels to prevent resource leaks

Changes

• Modified benchmark_algorithms() in benchmarking.jl to use timedwait()
• Removed the problematic task interruption logic
• Added proper channel cleanup

Testing

Tested the new implementation with various timeout scenarios:

• Tasks that complete before timeout ✓
• Tasks that exceed timeout ✓
• Edge cases with exact timing ✓

The autotune now properly handles timeouts without hanging, recording timed-out tests as NaN and continuing with the next algorithm.

Fixes the hanging issue reported after merging #716.