Move `modules/tokenizers` to be a subdir of `modules/transforms`

[joecummings]

We want to convey that tokenizers are a subset of transforms.

[Ankur-singh]

Hey @joecummings, I don't see anyone else working on this. I would like to give it a try.

[Ankur-singh]

Hey @joecummings, I created a PR (#2231) implementing the suggested changes. I was only able to test with Qwen2.5-0.5B model as I only have 8GBs GPU. Can you please try running other recipes using bigger models on a beefier machine.