Add integration test files for TPU v6e

[agrawalkhushi18]

This PR adds a build file and a test that verifies TPU v6e cluster provisioning, runs a simple JAX job, and tears down the cluster. The test uses a single-host, single-slice (2x2) topology and invokes the jax command to exercise the device count. I validated the change by running the test locally — it completed successfully.

Submission Checklist

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Please take the following actions before submitting this pull request.

• Fork your PR branch from the Toolkit "develop" branch (not main)
• Test all changes with pre-commit in a local branch #
• Confirm that "make tests" passes all tests
• Add or modify unit tests to cover code changes
• Ensure that unit test coverage remains above 80%
• Update all applicable documentation
• Follow Cluster Toolkit Contribution guidelines #

[SwarnaBharathiMantena]

LGTM