chore: update burn to v0.19.1 and remove outdated cudarc dependencies

- Bumped `burn` and `burn-import` workspace dependencies to v0.19.1.
- Removed redundant `cudarc` dependency and associated comments from examples.
- Streamlined ResNet-finetune learning rate scheduling with a new composed scheduler.
- Adjusted ResNet-finetune default arguments for training configuration: updated `warmup_epochs`, `batch_size`, `patience`, and others.

Author: crutcher