[FEATURE] Replace custom resource with deployspec command

**Describe the solution you'd like**
Simple custom resources are overkill and unnecessary tech debt. Replace [enable_custom_sagemaker_projects](https://github.com/awslabs/aiops-modules/blob/main/modules/sagemaker/sagemaker-studio/stack.py#L154) custom resource with command in the deployspec.

Start in modules/sagemaker/sagemaker-studio/stack.py at enable_custom_sagemaker_projects and trace how the custom resource is used. Then inspect the repository's deployspec command conventions. Done means the custom resource is replaced by an equivalent deployspec command without losing the requested SageMaker project setup behavior.

Written by the indexing model from the issue text.