gh-102024: Reduced _idle_semaphore.release calls (#102025)

Reduced _idle_semaphore.release calls in concurrent.futures.thread._worker
_idle_semaphore.release() is now only called if only work_queue is empty.

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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>