Add optimizer_cls_and_kwargs attribute to PPO and RLOO

[qgallouedec]

What does this PR do?

After huggingface/transformers#34358, a trainer has a self.optimizer_cls_and_kwargs. However, PPO and RLOO doesn't call super().__init__() in their __init__ method. Consequently, self.optimizer_cls_and_kwargs is not defined, resulting to

$ python examples/scripts/ppo/ppo.py --dataset_name trl-internal-testing/descriptiveness-sentiment-trl-style --dataset_train_split descriptiveness --learning_rate 3e-6 --output_dir models/minimal/ppo --per_device_train_batch_size 4     --gradient_accumulation_steps 1 --total_episodes 10 --model_name_or_path EleutherAI/pythia-14m --missing_eos_penalty 1.0 --save_strategy no --stop_token eos

Traceback (most recent call last):
  File "/fsx/qgallouedec/trl/examples/scripts/ppo/ppo.py", line 125, in <module>
    trainer = PPOTrainer(
              ^^^^^^^^^^^
  File "/fsx/qgallouedec/trl/trl/trainer/ppo_trainer.py", line 180, in __init__
    self.create_optimizer_and_scheduler(
  File "/fsx/qgallouedec/transformers/src/transformers/trainer.py", line 1138, in create_optimizer_and_scheduler
    self.create_optimizer()
  File "/fsx/qgallouedec/transformers/src/transformers/trainer.py", line 1183, in create_optimizer
    if self.optimizer_cls_and_kwargs is not None:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'PPOTrainer' object has no attribute 'optimizer_cls_and_kwargs'. Did you mean: 'get_optimizer_cls_and_kwargs'?

This PR fixes our CI "Tests with dev dependencies".

Mentioned here #2288 (comment)

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[lewtun]

LGTM!