fix: after serverless upgrade, GONE exceptions now throw an error

[andreabadesso]

Motivation

Fixes https://github.com/HathorNetwork/internal-issues/issues/275

In serverless v3, ApiGatewayManagementApiClient throws an error on failures, our code was not ready to handle them, so we were never handling GONE exceptions and old connections were stacking up in redis because of what is described in the issue above.

Acceptance Criteria

• We should be able to detect when a connection is already closed (GONE) and remove its handler from redis
• We should alert on unhandled errors
• We should include debug logs so we can keep track of how often this is happening (by filtering the log in cloudwatch)
• We should not throw in sendMessageToClient so that the SQS event is removed from the queue (and not retried)

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged
• Make sure either the unit tests and/or the QA tests are capable of testing the new features
• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.