port `t5` and `clip` to `nnx.Module`

[SauravMaheshkar]

Currently, we load the t5 and clip models as torch modules and wrap their outputs as JAX arrays. This prevents OOM during inference (since we can use the .to() method); having a pure JAX inference pipeline would be ideal.

References

1. Initialize Flax model params on CPU  huggingface/transformers#24711
2. feat(flax): leave restored weights on CPU huggingface/transformers#15295