feat(providers): Groq now uses LiteLLM openai-compat (#1303)

Groq has never supported raw completions anyhow. So this makes it easier
to switch it to LiteLLM. All our test suite passes.

I also updated all the openai-compat providers so they work with api
keys passed from headers. `provider_data`

## Test Plan

```bash
LLAMA_STACK_CONFIG=groq \
   pytest -s -v tests/client-sdk/inference/test_text_inference.py \
   --inference-model=groq/llama-3.3-70b-versatile --vision-inference-model=""
```

Also tested (openai, anthropic, gemini) providers. No regressions.

llama_stack/providers/remote/inference/groq/__init__.py

@@ -4,23 +4,14 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-from pydantic import BaseModel
-
 from llama_stack.apis.inference import Inference
 
 from .config import GroqConfig
 
 
-class GroqProviderDataValidator(BaseModel):
-    groq_api_key: str
-
-
 async def get_adapter_impl(config: GroqConfig, _deps) -> Inference:
     # import dynamically so the import is used only when it is needed
     from .groq import GroqInferenceAdapter
 
-    if not isinstance(config, GroqConfig):
-        raise RuntimeError(f"Unexpected config type: {type(config)}")
-
     adapter = GroqInferenceAdapter(config)
     return adapter