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/templates/vllm-gpu/build.yaml

@@ -15,15 +15,9 @@ distribution_spec:
     - inline::meta-reference
     telemetry:
     - inline::meta-reference
-    eval:
-    - inline::meta-reference
     datasetio:
     - remote::huggingface
     - inline::localfs
-    scoring:
-    - inline::basic
-    - inline::llm-as-judge
-    - inline::braintrust
     tool_runtime:
     - remote::brave-search
     - remote::tavily-search