feat: automated conda-forge release chain automation

[mollyheamazon]

Description:

Adds a GitHub Actions workflow to automate the conda-forge release chain for all SageMaker Python SDK subpackages. To use this feature, click on the run workflow button in actions in Conda Forge Release Chain tab, and wait for its completion.

The workflow triggers manually and orchestrates releases in dependency order: sagemaker-core → sagemaker-train → sagemaker-serve → sagemaker-mlops → sagemaker-python-sdk → sagemaker (meta).

Feedstocks:

• sagemaker-core-feedstock
• sagemaker-train-feedstock
• sagemaker-serve-feedstock
• sagemaker-mlops-feedstock
• sagemaker-python-sdk-feedstock
• sagemaker-feedstock

Previously, conda-forge releases required manual intervention on each feedstock PR.
Team runbook for conda-forge release

How it works:

For each package, the reusable workflow (_conda-forge-package-release.yml):

1. Waits for the upstream dependency to appear on conda-forge
2. Polls the feedstock PR, checking CI status each interval:
   • CI passing → merges the PR
   • CI failing → reruns failed jobs, waits for next cycle
   • CI pending → waits

Testing

Successful run in my fork

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