Build MaxText images in CI using stable/nightly mode

[SurbhiJainUSC]

Description

Refactor UploadDockerImages.yml to build MaxText images using stable/nightly MODE.
Fixes: b/470085466

Tests

Manually triggered the workflow
TPU image build: https://github.com/AI-Hypercomputer/maxtext/actions/runs/20347831817/job/58464575964
GPU image build: https://github.com/AI-Hypercomputer/maxtext/actions/runs/20349309276/job/58469459735
Note that GPU image build is failing because of transformer engine package, which should be fixed by #2833

Checklist

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• 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.

[khatwanimohit]

lgtm