feat: create HTTP DELETE API endpoints to unregister ScoringFn and Benchmark resources in Llama Stack (#3371)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
This PR provides functionality for users to unregister ScoringFn and
Benchmark resources for `scoring` and `eval` APIs.

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->
Closes #3051 

## Test Plan
<!-- Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->
Updated integration and unit tests via CI workflow

llama_stack/providers/inline/eval/meta_reference/eval.py

@@ -75,6 +75,13 @@ class MetaReferenceEvalImpl(
         )
         self.benchmarks[task_def.identifier] = task_def
 
+    async def unregister_benchmark(self, benchmark_id: str) -> None:
+        if benchmark_id in self.benchmarks:
+            del self.benchmarks[benchmark_id]
+
+        key = f"{EVAL_TASKS_PREFIX}{benchmark_id}"
+        await self.kvstore.delete(key)
+
     async def run_eval(
         self,
         benchmark_id: str,

llama_stack/providers/inline/scoring/llm_as_judge/scoring.py

@@ -63,6 +63,9 @@ class LlmAsJudgeScoringImpl(
     async def register_scoring_function(self, function_def: ScoringFn) -> None:
         self.llm_as_judge_fn.register_scoring_fn_def(function_def)
 
+    async def unregister_scoring_function(self, scoring_fn_id: str) -> None:
+        self.llm_as_judge_fn.unregister_scoring_fn_def(scoring_fn_id)
+
     async def score_batch(
         self,
         dataset_id: str,