Transition MaxText docker image build workflow to package-based installation

[SurbhiJainUSC]

Description

This PR transitions the nightly Docker image build workflow from a source-based installation to a package-based installation. This change is to standardize environment setups across all workflows by leveraging the MaxText Python package. Additionally, it introduces an automated notification system to track nightly build failures.

Key Changes

• Package-Based Build: Refactors "Build Images" workflow to install maxtext via PyPI (maxtext[runner]) rather than performing an editable source install from a local clone.
• Automated Failure Notifications: Added a new notify_failure job to the nightly workflow. This job is designed to create a new GitHub issue or update an existing one whenever a scheduled build fails.
• Standardization: Aligns the containerized environment with the recommended installation path, ensuring that Docker images match released package versions.

Why is this change being made?

1. Environment Consistency: The previous source-based build was fragmented and often led to inconsistencies between local user environments and containerized runs. By using the PyPI package, we ensure that both internal and external users have access to identical, reproducible environments.
2. Failure Tracking: Nightly build failures were previously difficult to monitor and often went untracked. The new notify_failure job provides immediate visibility into regressions by automating issue creation.

Tests

CI tests and https://github.com/AI-Hypercomputer/maxtext/actions/runs/25235820972

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[github-actions]

🤖 Hi @SurbhiJainUSC, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[github-actions]

## 📋 Review Summary

This PR successfully transitions the MaxText Docker image build process to a package-based installation, which improves consistency and maintainability. It also introduces a valuable automated failure notification system for nightly builds.

🔍 General Feedback

• Redundancy: The Copy tests assets to package directory step in the workflow is redundant because the Dockerfile already handles copying tests from the root context.
• Brittleness: Hardcoded Python version paths (python3.12) should be replaced with more dynamic alternatives to future-proof the workflows.
• Conventions: The change to image naming (adding an underscore before the suffix) and the use of short SHAs for tagging are positive improvements but should be noted as changes to existing conventions.
• Variables: Ensure vars.PROJECT_NAME is defined in the repository settings to prevent build failures.