fix!: update eval-tasks -> benchmarks (#1032)

# What does this PR do?

- Update `/eval-tasks` to `/benchmarks`
- ⚠️ Remove differentiation between `app` v.s. `benchmark` eval task
config. Now we only have `BenchmarkConfig`. The overloaded `benchmark`
is confusing and do not add any value. Backward compatibility is being
kept as the "type" is not being used anywhere.

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
- This change is backward compatible 
- Run notebook test with

```
pytest -v -s --nbval-lax ./docs/getting_started.ipynb
pytest -v -s --nbval-lax ./docs/notebooks/Llama_Stack_Benchmark_Evals.ipynb
```

<img width="846" alt="image"
src="https://github.com/user-attachments/assets/d2fc06a7-593a-444f-bc1f-10ab9b0c843d"
/>



[//]: # (## Documentation)
[//]: # (- [ ] Added a Changelog entry if the change is significant)

---------

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>
Signed-off-by: Ben Browning <bbrownin@redhat.com>
Signed-off-by: Sébastien Han <seb@redhat.com>
Signed-off-by: reidliu <reid201711@gmail.com>
Co-authored-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>
Co-authored-by: Ben Browning <ben324@gmail.com>
Co-authored-by: Sébastien Han <seb@redhat.com>
Co-authored-by: Reid <61492567+reidliu41@users.noreply.github.com>
Co-authored-by: reidliu <reid201711@gmail.com>
Co-authored-by: Yuan Tang <terrytangyuan@gmail.com>

llama_stack/distribution/stack.py

@@ -15,10 +15,10 @@ from termcolor import colored
 
 from llama_stack.apis.agents import Agents
 from llama_stack.apis.batch_inference import BatchInference
+from llama_stack.apis.benchmarks import Benchmarks
 from llama_stack.apis.datasetio import DatasetIO
 from llama_stack.apis.datasets import Datasets
 from llama_stack.apis.eval import Eval
-from llama_stack.apis.eval_tasks import EvalTasks
 from llama_stack.apis.inference import Inference
 from llama_stack.apis.inspect import Inspect
 from llama_stack.apis.models import Models
@@ -53,7 +53,7 @@ class LlamaStack(
     PostTraining,
     VectorIO,
     Eval,
-    EvalTasks,
+    Benchmarks,
     Scoring,
     ScoringFunctions,
     DatasetIO,
@@ -78,7 +78,7 @@ RESOURCES = [
         "register_scoring_function",
         "list_scoring_functions",
     ),
-    ("eval_tasks", Api.eval_tasks, "register_eval_task", "list_eval_tasks"),
+    ("benchmarks", Api.benchmarks, "register_benchmark", "list_benchmarks"),
     ("tool_groups", Api.tool_groups, "register_tool_group", "list_tool_groups"),
 ]