Added a task decorator for QWorkerd plugins

[ownaginatious]

Added a task decorator for qworkerd plugins with most settings already filled out. This is to reduce the amount of boiler plate code required for making a qworkerd plugin.

Syntax of the decorator is like this with default kwargs:

@qworkerd_task(base = QWTask, retry_on = (), no_retry_on = (), fail_handler = None)
def my_task(...):
   ...

To have a task only retry on RequestException and InconsistentException, and send to Sentry on all others, do:

@qworkerd_task(retry_on = (RequestException, InconsistentException))
def my_task(...):
   ...

To have a task retry on all exceptions except RequestException:

@qworkerd_task(no_retry_on = (RequestException,))
def my_task(...):
   ...

If nothing is specified, all exceptions will trigger retries:

@qworkerd_task()
def my_task(...):
   ...