[GRPO] switch grpo liger loss to triton version

[kashif]

What does this PR do?

Fixes dapo loss type support, but needs to wait for upstream merge and release linkedin/Liger-Kernel#939

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[kashif]

@lewtun would you be able to benchmark this branch for memory usage of grpo trainer?

[lewtun]

Thanks a lot for adding this @kashif ! LGTM with a question about adding 1 to logits_to_keep twice. Could you also add your nice plots showing the memory improvement with the Triton loss to the PR description?

Also, do we need to bump the minimum liger version?

[qgallouedec]

LGTM, it would be nice to have a quick comparison of the profiles, just to get an idea of the extent of the memory reduction.

[kashif]

comparison Red (old) and pink is triton based