More idiomatic REST API (#765)

# What does this PR do?

This PR changes our API to follow more idiomatic REST API approaches of
having paths being resources and methods indicating the action being
performed.

Changes made to generator:
1) removed the prefix check of "get" as its not required and is actually
needed for other method types too
2) removed _ check on path since variables can have "_"



## Test Plan

LLAMA_STACK_BASE_URL=http://localhost:5000 pytest -v
tests/client-sdk/agents/test_agents.py

llama_stack/apis/datasets/datasets.py

@@ -7,11 +7,9 @@
 from typing import Any, Dict, List, Literal, Optional, Protocol
 
 from llama_models.schema_utils import json_schema_type, webmethod
-
 from pydantic import BaseModel, Field
 
 from llama_stack.apis.common.content_types import URL
-
 from llama_stack.apis.common.type_system import ParamType
 from llama_stack.apis.resource import Resource, ResourceType
 
@@ -44,8 +42,12 @@ class DatasetInput(CommonDatasetFields, BaseModel):
     provider_dataset_id: Optional[str] = None
 
 
+class ListDatasetsResponse(BaseModel):
+    data: List[Dataset]
+
+
 class Datasets(Protocol):
-    @webmethod(route="/datasets/register", method="POST")
+    @webmethod(route="/datasets", method="POST")
     async def register_dataset(
         self,
         dataset_id: str,
@@ -56,16 +58,16 @@ class Datasets(Protocol):
         metadata: Optional[Dict[str, Any]] = None,
     ) -> None: ...
 
-    @webmethod(route="/datasets/get", method="GET")
+    @webmethod(route="/datasets/{dataset_id}", method="GET")
     async def get_dataset(
         self,
         dataset_id: str,
     ) -> Optional[Dataset]: ...
 
-    @webmethod(route="/datasets/list", method="GET")
-    async def list_datasets(self) -> List[Dataset]: ...
+    @webmethod(route="/datasets", method="GET")
+    async def list_datasets(self) -> ListDatasetsResponse: ...
 
-    @webmethod(route="/datasets/unregister", method="POST")
+    @webmethod(route="/datasets/{dataset_id}", method="DELETE")
     async def unregister_dataset(
         self,
         dataset_id: str,