feat: introduce API leveling, post_training, eval to v1alpha (#3449)

# What does this PR do?

Rather than have a single `LLAMA_STACK_VERSION`, we need to have a
`_V1`, `_V1ALPHA`, and `_V1BETA` constant.

This also necessitated addition of `level` to the `WebMethod` so that
routing can be handeled properly.


For backwards compat, the `v1` routes are being kept around and marked
as `deprecated`. When used, the server will log a deprecation warning.

Deprecation log:

<img width="1224" height="134" alt="Screenshot 2025-09-25 at 2 43 36 PM"
src="https://github.com/user-attachments/assets/0cc7c245-dafc-48f0-be99-269fb9a686f9"
/>

move:
1. post_training to `v1alpha` as it is under heavy development and not
near its final state
2. eval: job scheduling is not implemented. Relies heavily on the
datasetio API which is under development missing implementations of
specific routes indicating the structure of those routes might change.
Additionally eval depends on the `inference` API which is going to be
deprecated, eval will likely need a major API surface change to conform
to using completions properly

implements leveling in #3317 

note: integration tests will fail until the SDK is regenerated with
v1alpha/inference as opposed to v1/inference

## Test Plan

existing tests should pass with newly generated schema. Conformance will
also pass as these routes are not the ones we currently test for
stability

Signed-off-by: Charlie Doern <cdoern@redhat.com>

llama_stack/apis/synthetic_data_generation/synthetic_data_generation.py

@@ -10,6 +10,7 @@ from typing import Any, Protocol
 from pydantic import BaseModel
 
 from llama_stack.apis.inference import Message
+from llama_stack.apis.version import LLAMA_STACK_API_V1
 from llama_stack.schema_utils import json_schema_type, webmethod
 
 
@@ -59,7 +60,7 @@ class SyntheticDataGenerationResponse(BaseModel):
 
 
 class SyntheticDataGeneration(Protocol):
-    @webmethod(route="/synthetic-data-generation/generate")
+    @webmethod(route="/synthetic-data-generation/generate", level=LLAMA_STACK_API_V1)
     def synthetic_data_generate(
         self,
         dialogs: list[Message],