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/routers/__init__.py

@@ -11,8 +11,8 @@ from llama_stack.distribution.store import DistributionRegistry
 from llama_stack.providers.datatypes import Api, RoutingTable
 
 from .routing_tables import (
+    BenchmarksRoutingTable,
     DatasetsRoutingTable,
-    EvalTasksRoutingTable,
     ModelsRoutingTable,
     ScoringFunctionsRoutingTable,
     ShieldsRoutingTable,
@@ -33,7 +33,7 @@ async def get_routing_table_impl(
         "shields": ShieldsRoutingTable,
         "datasets": DatasetsRoutingTable,
         "scoring_functions": ScoringFunctionsRoutingTable,
-        "eval_tasks": EvalTasksRoutingTable,
+        "benchmarks": BenchmarksRoutingTable,
         "tool_groups": ToolGroupsRoutingTable,
     }