Revise autoscaling interface

[luke-lombardi]

• Bring back the QueueDepthAutoscaler
• Modify concurrency to be called workers
• Add unit tests for deployment autoscalers
• Modify stub config to have an autoscaler field
• Remove max_containers field from decorator
• Fix infinite scaling up for timed out tasks
• Lower default task_queue task expiration

from beta9 import Image, QueueDepthAutoscaler, task_queue

@task_queue(
    workers=2,
    image=Image(python_version="python3.8", python_packages=["pandas", "csaps"]),
    autoscaler=QueueDepthAutoscaler(max_containers=5, tasks_per_container=1),
)
def process_file(path: str):
    import pandas as pd

    print(pd)

    print("yep...")
    import time

    time.sleep(35)

    return {"path": path, "result": True}