get_steps_values & steps

[tdigangi]

Retrieve get_steps_values & steps from argv and some minor cleanup.

Verified with ray job submit below.

ray job submit --working-dir "." --runtime-env-json='{"excludes": [".github", "MaxText/test_assets", ".vscode", "test_assets", "getting_started", "end_to_end", "venv", ".git", "pedagogical_examples"],"includes":["assets/"]}' -- python3 MaxText/ray_trainer.py MaxText/configs/base.yml steps=10 steps_per_loop=60  base_output_directory=$OUTPUT_PATH dataset_path=$DATASET_PATH model_name=llama2-7b per_device_batch_size=2  max_target_length=8192 tokenizer_path="assets/tokenizer.llama2" reuse_example_batch=1 ici_fsdp_parallelism=-1 attention='flash' enable_checkpointing=false sa_block_q_dq=2048 sa_block_q_dkv=2048 sa_block_q=1024 profiler="xplane" use_iota_embed=true remat_policy=full gcs_metrics=false