feat(DMVP-5664): flagger operator integration

[mrdntgrn]

No description provided.

[what-the-diff]

PR Summary

• README Updates: Enhanced the documentation for the flagger module by capturing details related to new input variables in README.md.
• ALB Ingress Controller Updates: Revised the relevant conditions in alb-ingress-controller.tf to deploy ALB ingress controller only when enable_alb_ingress_controller is toggled on.
• Main File Updates: Improved main.tf to conditionally execute the flagger module, giving users more control.
• New Example Files: Contributed a series of example files to guide users to deploy an EKS cluster equipped with the Flagger operator. Files include 0-setup.tf and 1-example.tf available under examples/eks-with-flagger/ with an additional dedicated README.
• Flagger Module: Implemented a comprehensive flagger module that can integrate the Flagger operator for canary deployments, adorned with its own README, output information, and variable declarations.
• Helm Release Additions: Incorporated resources for deploying the Flagger and its load tester using Helm charts, supported by corresponding variables.
• New Configurations: Introduced fresh input variables for flagger, facilitating metric template and load tester configurations.
• Updates in values.yaml.tpl and variables.tf: Adapted values.yaml.tpl for effective Prometheus metrics scraping. Enhanced variables.tf by integrating new variables: enable_alb_ingress_controller for managing the ALB ingress controller, enable_external_secrets for controlling the external-secrets operator, and flagger that allows numerous configurations under the Flagger operator, such as enabling it, setting namespaces, handling custom configurations, and managing load tester options.
• New Metric Template Settings: Enclosed examples of metric template configurations encouraging efficient usage of Flagger.