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)

docs/source/distributions/self_hosted_distro/meta-reference-quantized-gpu.md

@@ -17,10 +17,8 @@ The `llamastack/distribution-meta-reference-quantized-gpu` distribution consists
 |-----|-------------|
 | agents | `inline::meta-reference` |
 | datasetio | `remote::huggingface`, `inline::localfs` |
-| eval | `inline::meta-reference` |
 | inference | `inline::meta-reference-quantized` |
 | safety | `inline::llama-guard` |
-| scoring | `inline::basic`, `inline::llm-as-judge`, `inline::braintrust` |
 | telemetry | `inline::meta-reference` |
 | tool_runtime | `remote::brave-search`, `remote::tavily-search`, `inline::code-interpreter`, `inline::rag-runtime`, `remote::model-context-protocol` |
 | vector_io | `inline::faiss`, `remote::chromadb`, `remote::pgvector` |