Issue #, if available:
#567

Description of changes:
Add CognitoUserPoolCustomSMSSender java lambda event.
I have added Response just to keep in line with other java events even though the custom SMS sender lambda doesn't need to return anything:

Amazon Cognito doesn't expect any additional return information in the response. Your function can use API operations to query and modify your resources, or record event metadata to an external system.

There are some more details in the issue #567

See more documentation on the Custom SMS Sender here: https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-custom-sms-sender.html

Target (OCI, Managed Runtime, both):

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