Fix: take last task from the pending tasks

[crismacv]

This PR fixes a scheduling issue that causes executors to spend time running tasks that are no longer needed, which reduces overall evaluation throughput.

Problem

Tasks are rotated from the front of the queue at every rotating_interval.
Executors also fetch tasks from the front.

When an executor cannot finish rotating_count tasks within one interval, tasks may be rotated before they are executed.
As a result, executors can spend time running tasks that are already outdated, which leads to unnecessarily low evaluation speed.

Solution

Executors now fetch tasks from the end of the queue instead of the front.
Rotation continues to operate on the front of the queue.

This prevents in-progress tasks from being removed and improves evaluation throughput.