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/tool_runtime/brave_search/brave_search.py

@@ -4,7 +4,7 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-from typing import Any, Dict, Optional
+from typing import Any
 
 import httpx
 
@@ -49,7 +49,7 @@ class BraveSearchToolRuntimeImpl(ToolsProtocolPrivate, ToolRuntime, NeedsRequest
         return provider_data.brave_search_api_key
 
     async def list_runtime_tools(
-        self, tool_group_id: Optional[str] = None, mcp_endpoint: Optional[URL] = None
+        self, tool_group_id: str | None = None, mcp_endpoint: URL | None = None
     ) -> ListToolDefsResponse:
         return ListToolDefsResponse(
             data=[
@@ -68,7 +68,7 @@ class BraveSearchToolRuntimeImpl(ToolsProtocolPrivate, ToolRuntime, NeedsRequest
             ]
         )
 
-    async def invoke_tool(self, tool_name: str, kwargs: Dict[str, Any]) -> ToolInvocationResult:
+    async def invoke_tool(self, tool_name: str, kwargs: dict[str, Any]) -> ToolInvocationResult:
         api_key = self._get_api_key()
         url = "https://api.search.brave.com/res/v1/web/search"
         headers = {

llama_stack/providers/remote/tool_runtime/brave_search/config.py

@@ -4,13 +4,13 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-from typing import Any, Dict, Optional
+from typing import Any
 
 from pydantic import BaseModel, Field
 
 
 class BraveSearchToolConfig(BaseModel):
-    api_key: Optional[str] = Field(
+    api_key: str | None = Field(
         default=None,
         description="The Brave Search API Key",
     )
@@ -20,7 +20,7 @@ class BraveSearchToolConfig(BaseModel):
     )
 
     @classmethod
-    def sample_run_config(cls, __distro_dir__: str) -> Dict[str, Any]:
+    def sample_run_config(cls, __distro_dir__: str) -> dict[str, Any]:
         return {
             "api_key": "${env.BRAVE_SEARCH_API_KEY:}",
             "max_results": 3,