Deprecate tpu maxtext candidate image and add JAII_candidate DAG

[Rohan-Bierneni]

Description

Since the public JAX AI Image will now have monthly ships with JAX releases, no longer need to use images built off the candidate image. Note that this is only for TPUs. GPUs will have monthly ships from next month onwards, and gpu_candidate flows will be deprecated then

Tests

Verified that latest public JAX AI Image works properly and maxtext images built with it are passing XLML tests.
Link to launchpad doc for testing the image.

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.