add cfn schema fetcher

[vicheey]

Issue #, if available

SAM's CFN schema used to pull the CFN schema update automatically in from awslabs/goformation repository. Refer to this diagram to understand more in detail on how the schema changes work.

The goformation repository was deprecated Oct 17, 2024. We have been doing manual update to pull the CFN schema change to update sam doc

Description of changes

• Add script that fetch CFN schema directly and generate cloudformation.schema.json (what we used to get from goformation package).
• Update Makefile script to fetch the CFN schema directly
• Add contract tests.

Description of how you validated changes

I compare the hash of the cloudformation.schema.json generated by the new python script with that generated from the original package. The contract test take the spec and ensure the generated schema match what expected.

Checklist

• Review the generative AI contribution guidelines
• Adheres to the development guidelines
• Add/update transform tests
  • Using correct values
  • Using wrong values
• Add/update integration tests

Examples?

Please reach out in the comments if you want to add an example. Examples will be
added to sam init through aws/aws-sam-cli-app-templates.

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