chore: move all Llama Stack types from llama-models to llama-stack (#1098)

llama-models should have extremely minimal cruft. Its sole purpose
should be didactic -- show the simplest implementation of the llama
models and document the prompt formats, etc.

This PR is the complement to
https://github.com/meta-llama/llama-models/pull/279

## Test Plan

Ensure all `llama` CLI `model` sub-commands work:

```bash
llama model list
llama model download --model-id ...
llama model prompt-format -m ...
```

Ran tests:
```bash
cd tests/client-sdk
LLAMA_STACK_CONFIG=fireworks pytest -s -v inference/
LLAMA_STACK_CONFIG=fireworks pytest -s -v vector_io/
LLAMA_STACK_CONFIG=fireworks pytest -s -v agents/
```

Create a fresh venv `uv venv && source .venv/bin/activate` and run
`llama stack build --template fireworks --image-type venv` followed by
`llama stack run together --image-type venv` <-- the server runs

Also checked that the OpenAPI generator can run and there is no change
in the generated files as a result.

```bash
cd docs/openapi_generator
sh run_openapi_generator.sh
```

llama_stack/schema_utils.py

@@ -0,0 +1,50 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from dataclasses import dataclass
+from typing import Any, Callable, List, Optional, TypeVar
+
+from .strong_typing.schema import json_schema_type, register_schema  # noqa: F401
+
+T = TypeVar("T")
+
+
+@dataclass
+class WebMethod:
+    route: Optional[str] = None
+    public: bool = False
+    request_examples: Optional[List[Any]] = None
+    response_examples: Optional[List[Any]] = None
+    method: Optional[str] = None
+
+
+def webmethod(
+    route: Optional[str] = None,
+    method: Optional[str] = None,
+    public: Optional[bool] = False,
+    request_examples: Optional[List[Any]] = None,
+    response_examples: Optional[List[Any]] = None,
+) -> Callable[[T], T]:
+    """
+    Decorator that supplies additional metadata to an endpoint operation function.
+
+    :param route: The URL path pattern associated with this operation which path parameters are substituted into.
+    :param public: True if the operation can be invoked without prior authentication.
+    :param request_examples: Sample requests that the operation might take. Pass a list of objects, not JSON.
+    :param response_examples: Sample responses that the operation might produce. Pass a list of objects, not JSON.
+    """
+
+    def wrap(cls: T) -> T:
+        cls.__webmethod__ = WebMethod(
+            route=route,
+            method=method,
+            public=public or False,
+            request_examples=request_examples,
+            response_examples=response_examples,
+        )
+        return cls
+
+    return wrap