Clean up Pax and TensorFlow PJRT nightly tests

[RissyRan]

Description

Clean up Pax and TensorFlow PJRT nightly tests (check the tests in onduty link have been onboarded):

• Pax tests have been fully onboarded to Airflow
• Tensorflow PJRT tests have been onboarded to Airflow: Keras & ResNet (DLRM is not working on PJRT yet)
• Clean up dashboard tabs (please note we will need to keep three jax integration test configs for now as Airflow imports the Jsonnet directly).

Tests

Please describe the tests that you ran on TPUs to verify changes.

Instruction and/or command lines to reproduce your tests: ...
Expect all checks pass

List links for your tests (use go/shortn-gen for any internal link): ...

Checklist

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

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run one-shot tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed.