Decouple printing logs to stdout from tensorboard

[pavanholla]

Commit 7bc0f48 introduced a config to disable tensorboard. However, it unintentionally disable printing to stdout as well. This CL separates the logic that prints logs from the logic the writes to tensorboard.

Test:
Check that enable_tensorboard=False and enable_tensorboard=True lead to the same logs on stdout.

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[bvandermoon]

Is it necessary to gate the logging with with jax.spmd_mode("allow_all") and if metrics to write? I see a duplicate PR was created that isn't gating with those. Are the extra conditions needed here?