feat!: Add aws-lambda-powertools support, use GitHub app webhook in place of deprecated standalone webhook

[bryantbiggs]

Description

🚧 TODO 🚧

• Replace standard logger with aws-lambda-power tools structured logger
  • Add docs on Gov Cloud caveat and work around until natively supported
• Update to use Slack App webhook; removing legacy incoming, standalone webhook (closes Legacy Incoming Webhooks vs. Slack Apps #86)
• Add support for pulling Slack details from
  • SSM parameter store (closes feat: make it possible to use ssm parameters as slack_webhook_url #107)
  • Secrets Manager
  • Remove support for KMS encrypted env var
• Add support for EC2 autoscaling events (closes update Lambda function to handle an ASG notification #28 feat: Improved format of Auto Scaling notifications #76)
• Add support for proper name prefixes (closes [enhancement] Use name_prefix for cloudwatch log group to avoid namespace collisions #111)
• Ensure function execution result is propagated correctly (closes Exit code 1 on errors #91)
• Ensure proper headers are forwarded in request (closes feat: Add Content-Type and Content-Length on request #147)
• Add support for event source data classes
  • EC2 Autoscaling event
  • CloudWatch Alarm event
  • GuardDuty finding event
  • RDS events
  • Systems manager event
  • These

Motivation and Context

Breaking Changes

Yes

How Has This Been Tested?

• I have tested and validated these changes using one or more of the provided examples/* projects

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[bryantbiggs]

Shhhhh