Add tokenizer_kwargs argument to the text generation pipeline

[Joshua-Chin]

What does this PR do?

This PR adds a tokenizer_kwargs argument to the TextGenerationPipeline, allowing users to pass arbitrary arguments to the tokenizer during preprocessing. In particular, this lets users set chat template arguments, such as the enable_thinking flag for Qwen3 or SmolLM3.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

[Joshua-Chin]

The test failure seems to be an unrelated flake:

self = <test_accelerate_examples.ExamplesTestsNoTrainer testMethod=test_run_swag_no_trainer>

    @mock.patch.dict(os.environ, {"WANDB_MODE": "offline", "DVCLIVE_TEST": "true"})
    def test_run_swag_no_trainer(self):
        tmp_dir = self.get_auto_remove_tmp_dir()
        testargs = f"""
            {self.examples_dir}/pytorch/multiple-choice/run_swag_no_trainer.py
            --model_name_or_path google-bert/bert-base-uncased
            --train_file tests/fixtures/tests_samples/swag/sample.json
            --validation_file tests/fixtures/tests_samples/swag/sample.json
            --output_dir {tmp_dir}
            --max_train_steps=20
            --num_warmup_steps=2
            --learning_rate=2e-4
            --per_device_train_batch_size=2
            --per_device_eval_batch_size=1
            --with_tracking
        """.split()
    
        run_command(self._launch_args + testargs)
        result = get_results(tmp_dir)
>       self.assertGreaterEqual(result["eval_accuracy"], 0.8)
E       AssertionError: 0.4 not greater than or equal to 0.8

examples/pytorch/test_accelerate_examples.py:225: AssertionError

Pushing an empty commit to re-run the CI.

[Joshua-Chin]

A disjoint set of tests have failed in the re-run.

[Joshua-Chin]

@Rocketknight1 Please review this PR when you have a chance. The CI failures seem to be caused by unrelated, flaky tests.

[Rocketknight1]

This LGTM! cc @gante just in case you have opinions about the max_length generate kwarg clash.

[Rocketknight1]

Also @Joshua-Chin you may need to rebase to fix some conflicts before we can merge the PR! That should also clear up the CI issues.

[gante]

One question about variable names, otherwise lgtm :)

[gante]

perhaps tokenizer_encode_kwargs? There are also kwargs used at decode time, and we don't want to mix the two

cc @Rocketknight1

[Joshua-Chin]

@gante I updated the argument to tokenizer_encode_kwargs. Please take another look when you have a chance.

[Joshua-Chin]

The CI is currently failing because of the following test, added by a recently merged change (HunYuan opensource #39606):

FAILED tests/models/hunyuan_v1_moe/test_modeling_hunyuan_v1_moe.py::HunYuanMoEV1ModelTest::test_generate_compile_model_forward_fullgraph - torch._dynamo.exc.Unsupported: Dynamic shape operator