Migrate to `asyncio.TaskGroup` for batch processing once Python 3.10 is dropped

[vdusek]

Summary

Once we drop support for Python 3.10, we should migrate the batch processing in request_queue.py to use asyncio.TaskGroup (available in Python 3.11+) for better error handling and cleaner code.

Current Implementation

The current batch processing pattern (around lines 855-870) uses manual task management:

tasks = set[asyncio.Task]()
for i in range(max_parallel):
    task = asyncio.create_task(coro, name=f'worker_{i}')
    tasks.add(task)
await asyncio_queue.join()
for task in tasks:
    task.cancel()
results = await asyncio.gather(*tasks)

Proposed Improvement

Use asyncio.TaskGroup for cleaner code and automatic exception handling:

async with asyncio.TaskGroup() as tg:
    workers = [
        tg.create_task(self._batch_add_requests_worker(queue, params))
        for _ in range(max_parallel)
    ]
    await asyncio_queue.join()
    for worker in workers:
        worker.cancel()
# TaskGroup automatically waits and handles exceptions properly

Benefits

• Better error handling: TaskGroup automatically propagates exceptions from any task
• Cleaner code: Context manager pattern ensures proper cleanup
• More Pythonic: Uses modern Python async patterns
• Automatic waiting: No need for explicit asyncio.gather() call

Prerequisites

• Drop support for Python 3.10 (TaskGroup requires Python 3.11+)