Add consumer with idle trigger

[danielle-tfh]

Notes

• add a consumer with idle trigger. This consumer is identical the other SQS consumer but with an added feature of triggering logic after a certain idle time has been reached.
  • the idle trigger is triggered if no new message has been received.
• This is a feature needed for MPCv2 where it relies on consistent traffic to know when to process requests in batch. If there is a sudden decrease in traffic, some old requests which were waiting to be batched could not be triggered until a new requests arrives.
  Note: We can not add a timeout in MPCv2 since it would require that all nodes timeout at the same time or they could go out of sync
• POC PR can be found here: https://github.com/worldcoin/signup-service/pull/828