Revert "use Pytree as base type in nnx_wrappers"

[gulsumgudukbay]

Description

This reverts commit 8840296. This commit was using Pytree as base type in nnx_wrappers. Currently, with JAX 0.6.0 on ROCm, the latest flax version supported is 0.10.7, hence this commit is not valid and breaks the execution.

Note: This commit should be reverted when flax version is upgraded to anything >= 0.11.0. Right now, JAX 0.6.0 does not support any flax version >= 0.10.7, hence this commit is required as flax started exposing PyTree after 0.11.0.

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Tests

I ran train.py with the following args:
python -m MaxText.train MaxText/configs/base.yml run_name=test hardware=gpu steps=5 model_name=llama2-7b attention=cudnn_flash_te enable_checkpointing=False ici_expert_parallelism=1 ici_fsdp_parallelism=-1 ici_data_parallelism=1 remat_policy=minimal scan_layers=True dataset_type=synthetic logits_dot_in_fp32=False dtype=bfloat16 weight_dtype=bfloat16 per_device_batch_size=1 max_target_length=2048 shardy=False

It was able to successfully complete execution.

Checklist

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• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed.