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)

tests/integration/scoring/test_scoring.py

@@ -43,12 +43,14 @@ def register_scoring_function(
     )
 
 
+@pytest.mark.skip(reason="TODO(xiyan): fix this")
 def test_scoring_functions_list(llama_stack_client):
     response = llama_stack_client.scoring_functions.list()
     assert isinstance(response, list)
     assert len(response) > 0
 
 
+@pytest.mark.skip(reason="TODO(xiyan): fix this")
 def test_scoring_functions_register(
     llama_stack_client,
     sample_scoring_fn_id,
@@ -81,6 +83,7 @@ def test_scoring_functions_register(
 
 
 @pytest.mark.parametrize("scoring_fn_id", ["basic::equality"])
+@pytest.mark.skip(reason="TODO(xiyan): fix this")
 def test_scoring_score(llama_stack_client, scoring_fn_id):
     # scoring individual rows
     df = pd.read_csv(Path(__file__).parent.parent / "datasets" / "test_dataset.csv")
@@ -100,6 +103,7 @@ def test_scoring_score(llama_stack_client, scoring_fn_id):
         assert len(response.results[x].score_rows) == len(rows)
 
 
+@pytest.mark.skip(reason="TODO(xiyan): fix this")
 def test_scoring_score_with_params_llm_as_judge(
     llama_stack_client,
     sample_judge_prompt_template,
@@ -139,6 +143,7 @@ def test_scoring_score_with_params_llm_as_judge(
         "braintrust",
     ],
 )
+@pytest.mark.skip(reason="TODO(xiyan): fix this")
 def test_scoring_score_with_aggregation_functions(
     llama_stack_client,
     sample_judge_prompt_template,