Add template to deploy to ECS

What does this MR do?

This MR adds a new CI template named Deploy-ECS.gitlab-ci.yml. This template can be used to deploy a Dockerized application to ECS as a review app.

The following snippet can be added to the .gitlab-ci.yml file of any project to perform such deployment:

stages:
  - build
  - review

variables:
  CLUSTER: my-ecs
  SERVICE: my-service
  TASK_DEFINITION: my-task-definition

include:
  - template: Deploy-ECS.gitlab-ci.yml

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #207962 (closed)