fix: Pass policy.logprob_chunk_size to loss functions

[pjin-nvidia]

What does this PR do ?

The policy.logprob_chunk_size config value was not being passed to loss functions which directly call from_parallel_logits_to_logprobs or get_logprobs_from_vocab_parallel_logits, causing OOMs in some training run configurations.

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[github-actions]

ℹ️ File Consistency Check

Check based on commit: d22624e (PR #1295 from pjin/chunk-size)

✅ DTensor Policy Worker Synchronization Check

Both DTensor policy worker files were modified in this PR:

• nemo_rl/models/policy/dtensor_policy_worker.py
• nemo_rl/models/policy/dtensor_policy_worker_v2.py

Please ensure that the changes are consistent between both files where applicable.

---

_{This check ensures that related file implementations remain synchronized across the codebase. If you believe this warning is incorrect or the files should intentionally differ, please add a comment explaining the reasoning.}

[github-actions]

ℹ️ File Consistency Check

Check based on commit: b962760 (PR #1295 from pjin/chunk-size)

✅ DTensor Policy Worker Synchronization Check

Both DTensor policy worker files were modified in this PR:

• nemo_rl/models/policy/dtensor_policy_worker.py
• nemo_rl/models/policy/dtensor_policy_worker_v2.py

Please ensure that the changes are consistent between both files where applicable.

---

_{This check ensures that related file implementations remain synchronized across the codebase. If you believe this warning is incorrect or the files should intentionally differ, please add a comment explaining the reasoning.}

[github-actions]

ℹ️ File Consistency Check

Check based on commit: 2469dec (PR #1295 from pjin/chunk-size)

✅ DTensor Policy Worker Synchronization Check

Both DTensor policy worker files were modified in this PR:

• nemo_rl/models/policy/dtensor_policy_worker.py
• nemo_rl/models/policy/dtensor_policy_worker_v2.py

Please ensure that the changes are consistent between both files where applicable.

---

_{This check ensures that related file implementations remain synchronized across the codebase. If you believe this warning is incorrect or the files should intentionally differ, please add a comment explaining the reasoning.}