Add StableLM model for ONNX export testing

This commit adds the StableLM model `"hf-internal-testing/tiny-random-StableLmForCausalLM"` to the dictionaries of models for testing PyTorch ONNX export:

  * `PYTORCH_EXPORT_MODELS_TINY`
  * `PYTORCH_EXPORT_MODELS_LARGE`

This allows for including StableLM in regression tests to ensure compatibility with the updated ONNX exporter.

tests/exporters/exporters_utils.py

@@ -140,6 +140,7 @@
     "segformer": "hf-internal-testing/tiny-random-SegformerModel",
     "splinter": "hf-internal-testing/tiny-random-SplinterModel",
     "squeezebert": "hf-internal-testing/tiny-random-SqueezeBertModel",
+    "stablelm": "hf-internal-testing/tiny-random-StableLmForCausalLM",
     "swin": "hf-internal-testing/tiny-random-SwinModel",
     "swin2sr": "hf-internal-testing/tiny-random-Swin2SRModel",
     "t5": "hf-internal-testing/tiny-random-t5",
@@ -255,6 +256,7 @@
     "segformer": "nvidia/segformer-b0-finetuned-ade-512-512",
     "splinter": "hf-internal-testing/tiny-random-SplinterModel",
     "squeezebert": "squeezebert/squeezebert-uncased",
+    "stablelm": "hf-internal-testing/tiny-random-StableLmForCausalLM",
     "swin": "microsoft/swin-tiny-patch4-window7-224",
     "t5": "t5-small",
     "table-transformer": "microsoft/table-transformer-detection",