Unable to increase context length in SM serverless customizations

**Describe the feature you'd like**
Currently customers cannot use GRPO for Qwen model customization for models using long context (more than 2048 tokens)

**How would this feature be used? Please describe.**
Should work similar to JumpStart training implementation:
estimator = JumpStartEstimator(
model_id="meta-textgeneration-llama-2-7b",
hyperparameters={
"max_input_length": "4096", # Update context length here
"max_total_tokens": "4096"
}
)

**Describe alternatives you've considered**
Using SM training jobs for GRPO training with recipes.

**Additional context**
Customer: Intuit (a high-priority issue blocking usage of SM serverless customization service).