fix(stepfunctions-tasks): missing permissions for running tasks on ecs (#27891)

While working on [#27803](#27803), I noticed the integration tests for `aws-stepfunctions-tasks/ecs` were not fully working (they deployed but the state machines did not run successfully). This PR addresses two issues:

1. Missing permissions for `ecs:RunTask` on the task definition version.
<img width="1587" alt="sfn-role" src="https://github.com/aws/aws-cdk/assets/3310356/13a0d402-8cbb-4852-9708-290f3a3b6711">

2. The sample container was from a Lambda image. This resulted in the following error: `entrypoint requires the handler name to be the first argument`. I changed the image to `docker/library/python:3.12`.

These changes result in the successful execution of all four state machines in `aws-stepfunctions-tasks/ecs`.


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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: msambol

packages/@aws-cdk-testing/framework-integ/test/aws-stepfunctions-tasks/test/ecs/eventhandler-image/Dockerfile

@@ -1,5 +1,3 @@
-FROM public.ecr.aws/lambda/python:3.6
-EXPOSE 8000
-WORKDIR /src
-ADD . /src
-CMD python3 index.py
+FROM public.ecr.aws/docker/library/python:3.12
+ADD index.py .
+CMD [ "python3", "./index.py" ]

packages/@aws-cdk-testing/framework-integ/test/aws-stepfunctions-tasks/test/ecs/eventhandler-image/index.py

@@ -1,4 +1,3 @@
-#!/usr/bin/python
 import os
 import pprint