[AWSCORE-697] Add versioning to quickstart template

[dhan0779]

Note: Please remember to review the contribution guidelines
if you have not yet done so.

What does this PR do?

This PR modifies the release script for the cloudformation quickstart template to upload its latest version to the datadog-opensource-asset-versions bucket. The version information is stored in quickstart/versions.json:

{
  "latest": {
    "version": "v4.3.1",
    "release_date": "2026-02-03"
  }
}

Testing Guidelines

I tested the release script using the aws-ints-playground account:
aws-vault exec sso-aws-ints-team-playground-account-admin -- ./release.sh quickstart-test2 --private

I verified that the version gets uploaded to a test bucket: https://us-east-1.console.aws.amazon.com/s3/buckets/datadog-opensource-asset-versions-test2?region=us-east-1&tab=objects

Additional Notes

Anything else we should know when reviewing?