feat(eval api): (2.2/n) delete eval / scoring / scoring_fn apis (#1700)

# What does this PR do?
- To make it easier, delete existing `eval/scoring/scoring_function`
apis. There will be a bunch of broken impls here. The sequence is:
1. migrate benchmark graders
2. clean up existing scoring functions

- Add a skeleton evaluation impl to make tests pass. 

## Test Plan
tested in following PRs

[//]: # (## Documentation)

llama_stack/distribution/routers/__init__.py

@@ -14,7 +14,6 @@ from .routing_tables import (
     BenchmarksRoutingTable,
     DatasetsRoutingTable,
     ModelsRoutingTable,
-    ScoringFunctionsRoutingTable,
     ShieldsRoutingTable,
     ToolGroupsRoutingTable,
     VectorDBsRoutingTable,
@@ -32,7 +31,6 @@ async def get_routing_table_impl(
         "models": ModelsRoutingTable,
         "shields": ShieldsRoutingTable,
         "datasets": DatasetsRoutingTable,
-        "scoring_functions": ScoringFunctionsRoutingTable,
         "benchmarks": BenchmarksRoutingTable,
         "tool_groups": ToolGroupsRoutingTable,
     }
@@ -48,10 +46,8 @@ async def get_routing_table_impl(
 async def get_auto_router_impl(api: Api, routing_table: RoutingTable, deps: Dict[str, Any]) -> Any:
     from .routers import (
         DatasetIORouter,
-        EvalRouter,
         InferenceRouter,
         SafetyRouter,
-        ScoringRouter,
         ToolRuntimeRouter,
         VectorIORouter,
     )
@@ -61,8 +57,6 @@ async def get_auto_router_impl(api: Api, routing_table: RoutingTable, deps: Dict
         "inference": InferenceRouter,
         "safety": SafetyRouter,
         "datasetio": DatasetIORouter,
-        "scoring": ScoringRouter,
-        "eval": EvalRouter,
         "tool_runtime": ToolRuntimeRouter,
     }
     api_to_deps = {