Allow option to provision other CI tools than CodeBuild

[zeagord]

Describe the outcome you'd like

• Most of the times, there are instances where you have to use a CI/CD tool other than AWS CodeBuild like Gitlab CI, Github Actions, Jenkins, etc
• Allow an option to customize the CI stages or steps such showing a Terraform Plan or using tools like tfsec or tflint

Is your feature request related to a problem you are currently experiencing? If so, please describe. Unable to update the pipeline steps to use the private registries Additional context

Add any other context or screenshots about the feature request here.

Related to https://github.com/aws-ia/terraform-aws-control_tower_account_factory/issues/376

[snebhu3]

@zeagord thank you for reaching out and providing context about your use case. I have created an internal backlog to address this.

[BroodingMawlek]

100% agree, this is my use case right now.