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/post_training/post_training.py

@@ -6,16 +6,13 @@
 
 from datetime import datetime
 from enum import Enum
-
 from typing import Any, Dict, List, Literal, Optional, Protocol, Union
 
 from llama_models.schema_utils import json_schema_type, webmethod
-
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
 
 from llama_stack.apis.common.content_types import URL
-
 from llama_stack.apis.common.job_types import JobStatus
 from llama_stack.apis.common.training_types import Checkpoint
 
@@ -159,6 +156,10 @@ class PostTrainingJobStatusResponse(BaseModel):
     checkpoints: List[Checkpoint] = Field(default_factory=list)
 
 
+class ListPostTrainingJobsResponse(BaseModel):
+    data: List[PostTrainingJob]
+
+
 @json_schema_type
 class PostTrainingJobArtifactsResponse(BaseModel):
     """Artifacts of a finetuning job."""
@@ -197,7 +198,7 @@ class PostTraining(Protocol):
     ) -> PostTrainingJob: ...
 
     @webmethod(route="/post-training/jobs", method="GET")
-    async def get_training_jobs(self) -> List[PostTrainingJob]: ...
+    async def get_training_jobs(self) -> ListPostTrainingJobsResponse: ...
 
     @webmethod(route="/post-training/job/status", method="GET")
     async def get_training_job_status(