Add requeue command

[nefrathenrici]

Overview

This PR adds rqrun, a new tool that automatically handles job requeueing/retry logic for SLURM (sbatch) and PBS (qsub) schedulers. The tool wraps user scripts with signal handling to automatically resubmit jobs when they receive timeout or preemption signals. The number of retries can be controlled by an environment variable, RQ_RETRY_LIMIT

How It Works

1. User calls rqrun sbatch ... script.sh or rqrun qsub ... script.sh
2. rqrun creates a wrapper script that:
   • Traps timeout/preemption signals (SIGUSR1 for Slurm, TERM for PBS)
   • Runs the user's original script
   • Automatically resubmits the job when signals are received
   • Tracks retry attempts via environment variables
3. The wrapper script is submitted to the scheduler
4. If the job times out or is preempted, the signal is intercepted and the job is resubmitted.
5. Process continues until the job completes successfully or retry limit is reached