chore: enable pyupgrade fixes (#1806)

# What does this PR do?

The goal of this PR is code base modernization.

Schema reflection code needed a minor adjustment to handle UnionTypes
and collections.abc.AsyncIterator. (Both are preferred for latest Python
releases.)

Note to reviewers: almost all changes here are automatically generated
by pyupgrade. Some additional unused imports were cleaned up. The only
change worth of note can be found under `docs/openapi_generator` and
`llama_stack/strong_typing/schema.py` where reflection code was updated
to deal with "newer" types.

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>

llama_stack/providers/remote/vector_io/chroma/chroma.py

@@ -6,7 +6,7 @@
 import asyncio
 import json
 import logging
-from typing import Any, Dict, List, Optional, Union
+from typing import Any
 from urllib.parse import urlparse
 
 import chromadb
@@ -27,7 +27,7 @@ from .config import ChromaVectorIOConfig as RemoteChromaVectorIOConfig
 log = logging.getLogger(__name__)
 
 
-ChromaClientType = Union[chromadb.AsyncHttpClient, chromadb.PersistentClient]
+ChromaClientType = chromadb.AsyncHttpClient | chromadb.PersistentClient
 
 
 # this is a helper to allow us to use async and non-async chroma clients interchangeably
@@ -42,7 +42,7 @@ class ChromaIndex(EmbeddingIndex):
         self.client = client
         self.collection = collection
 
-    async def add_chunks(self, chunks: List[Chunk], embeddings: NDArray):
+    async def add_chunks(self, chunks: list[Chunk], embeddings: NDArray):
         assert len(chunks) == len(embeddings), (
             f"Chunk length {len(chunks)} does not match embedding length {len(embeddings)}"
         )
@@ -89,7 +89,7 @@ class ChromaIndex(EmbeddingIndex):
 class ChromaVectorIOAdapter(VectorIO, VectorDBsProtocolPrivate):
     def __init__(
         self,
-        config: Union[RemoteChromaVectorIOConfig, InlineChromaVectorIOConfig],
+        config: RemoteChromaVectorIOConfig | InlineChromaVectorIOConfig,
         inference_api: Api.inference,
     ) -> None:
         log.info(f"Initializing ChromaVectorIOAdapter with url: {config}")
@@ -137,8 +137,8 @@ class ChromaVectorIOAdapter(VectorIO, VectorDBsProtocolPrivate):
     async def insert_chunks(
         self,
         vector_db_id: str,
-        chunks: List[Chunk],
-        ttl_seconds: Optional[int] = None,
+        chunks: list[Chunk],
+        ttl_seconds: int | None = None,
     ) -> None:
         index = await self._get_and_cache_vector_db_index(vector_db_id)
 
@@ -148,7 +148,7 @@ class ChromaVectorIOAdapter(VectorIO, VectorDBsProtocolPrivate):
         self,
         vector_db_id: str,
         query: InterleavedContent,
-        params: Optional[Dict[str, Any]] = None,
+        params: dict[str, Any] | None = None,
     ) -> QueryChunksResponse:
         index = await self._get_and_cache_vector_db_index(vector_db_id)