New infra compatibility updates

[dlutsch]

Description

Changes to allow ef-open to reference services deployed with serverless / k8s for the purpose of service to service communication.

• Update the aws:ec2:security-group/security-group-id lookup to search by name tag if the sg name isn't found.
• Add a "NoValue" default lookup value which will render to { "Ref": "AWS::NoValue" } if the lookup fails. This is a failsafe to prevent templates from failing to deploy if a lookup target doesn't exist yet in a given environment.
• Adds a new {{ENV_NEW}} symbol which will resolve to the matching new env name, based on values from the ef_site_config. i.e.

  "alpha" -> "sbx"
  "proto" -> "dev"
  "staging" -> "stg"
  "prod" -> "prd" 

• Removes the gitleaks github action. This was added a long time ago by security, but we do not appear to have an active license, and anyone involved with adding it has long since left the company.

Can this PR be merged / deployed at any time?

• Yes
• No, only at specific time (please specify below)
• No, only after certain conditions are met (please specify below)

Timeframe/Conditions:

How was this tested?

Tested using the sg lookup "cr-pay-transaction-service-stg" which is a serverless framework created security group, which references a name tag, not the sg name directly.