add brave tool provider (#653)

# What does this PR do?

Adds a new brave tool provider


## Test Plan

```
curl -X POST 'http://localhost:5000/alpha/toolgroups/register' \
-H 'Content-Type: application/json' \
-d '{
  "name": "search",
  "tool_group": {
    "type": "user_defined",
    "tools": [
      {
        "name": "brave_search",
        "description": "A web search tool",
        "parameters": [
          {
            "name": "query",
            "parameter_type": "string",
            "description": "The query to search"
          }
        ],
        "metadata": {},
        "tool_prompt_format": "json"
      }
    ]
  }
}'

curl -X POST 'http://localhost:5000/alpha/tool-runtime/invoke' \
-H 'Content-Type: application/json' \
-d '{
    "tool_id": "brave_search",
    "args": {
        "query": "who is meta ceo"
    }
}' | jq .content
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1973  100  1884  100    89  11288    533 --:--:-- --:--:-- --:--:-- 11885
"{'title': 'Mark Zuckerberg, Founder, Chairman and Chief Executive ...', 'url': 'https://about.meta.com/media-gallery/executives/mark-zuckerberg/', 'description': 'Not Logged In · Please log in to see this page', 'type': 'search_result'}\n{'title': 'Meta - Leadership & Governance', 'url': 'https://investor.fb.com/leadership-and-governance/', 'description': '<strong>Mark Zuckerberg</strong> is the founder, chairman and CEO of Meta, which he originally founded as Facebook in 2004. Mark is responsible for setting the overall direction and product strategy for the company. He leads the design of Meta&#x27;s services and development of its core technology and infrastructure.', 'type': 'search_result'}\n[{'type': 'video_result', 'url': '2372542949/', 'title': 'Mark Zuckerberg, the CEO of Meta, has officially joined the ...', 'description': \"Express Tribune, Karachi, Pakistan. 2,334,400 likes · 36,360 talking about this · 205 were here. The Express Tribune is Pakistan's #1 brand for breaking news in politics, sports, business, lifestyle\"}, {'type': 'video_result', 'url': 'https://www.youtube.com/watch?v=Y3oeQqtRvqk', 'title': \"Meta CEO: Mark Zuckerberg becomes World's Second Richest Person!\", 'description': 'Try VectorVest Risk-Free ➥➥➥ https://www.vectorvest.com/YTUse this link for a FREE Stock Analysis Report ➥➥➥ vectorvest.com/YTFSAVectorVest Merch Store ➥➥➥'}, {'type': 'video_result', 'url': '5348412224/', 'title': '#WATCH | Meta founder and CEO Mark Zuckerberg recently ...', 'description': 'See posts, photos and more on Facebook'}]"

curl -X POST 'http://localhost:5000/alpha/tool-runtime/invoke' \
-H 'Content-Type: application/json' -H 'X-LlamaStack-ProviderData: {"api_key": "<KEY>"}' \
-d '{
    "tool_id": "brave_search",
    "args": {
        "query": "who is meta ceo"
    }
}'
```

llama_stack/distribution/routers/routing_tables.py

@@ -108,6 +108,8 @@ class CommonRoutingTableImpl(RoutingTable):
                 await add_objects(scoring_functions, pid, ScoringFn)
             elif api == Api.eval:
                 p.eval_task_store = self
+            elif api == Api.tool_runtime:
+                p.tool_store = self
 
     async def shutdown(self) -> None:
         for p in self.impls_by_provider_id.values():
@@ -129,6 +131,8 @@ class CommonRoutingTableImpl(RoutingTable):
                 return ("Scoring", "scoring_function")
             elif isinstance(self, EvalTasksRoutingTable):
                 return ("Eval", "eval_task")
+            elif isinstance(self, ToolsRoutingTable):
+                return ("Tools", "tool")
             else:
                 raise ValueError("Unknown routing table type")
 
@@ -476,34 +480,40 @@ class ToolsRoutingTable(CommonRoutingTableImpl, Tools):
 
     async def register_tool_group(
         self,
-        name: str,
         tool_group: ToolGroup,
         provider_id: Optional[str] = None,
     ) -> None:
         tools = []
         if isinstance(tool_group, MCPToolGroup):
-            # TODO: first needs to be resolved to corresponding tools available in the MCP server
-            raise NotImplementedError("MCP tool provider not implemented yet")
+            # TODO: Actually find the right MCP provider
+            if provider_id is None:
+                raise ValueError("MCP provider_id not specified")
+            tools = await self.impls_by_provider_id[provider_id].discover_tools(
+                tool_group
+            )
+            for tool in tools:
+                tool.provider_id = provider_id
         elif isinstance(tool_group, UserDefinedToolGroup):
             for tool in tool_group.tools:
 
                 tools.append(
                     Tool(
                         identifier=tool.name,
-                        tool_group=name,
+                        tool_group=tool_group.name,
                         name=tool.name,
                         description=tool.description,
                         parameters=tool.parameters,
                         provider_id=provider_id,
                         tool_prompt_format=tool.tool_prompt_format,
                         provider_resource_id=tool.name,
+                        metadata=tool.metadata,
                     )
                 )
         else:
             raise ValueError(f"Unknown tool group: {tool_group}")
 
         for tool in tools:
-            existing_tool = await self.get_tool(tool.name)
+            existing_tool = await self.get_tool(tool.identifier)
             # Compare existing and new object if one exists
             if existing_tool:
                 # Compare all fields except provider_id since that might be None in new obj