Add adapter to use MCP servers as tools

[marcusschiesser]

add mcp to @llamaindex/tool package:

for using stdio mcp:

const server = mcp({
  command: "npx",
  args: ["-y", "@modelcontextprotocol/server-filesystem"],
  env: ...
});

for using sse mcp:

const server = mcp({
  url: "http://localhost:3000/sse",
  env: ...
});

for using the tools provided by the mcp servers:

const myAgent = agent({
  name: "Assistant",
  systemPrompt: `Use the tools to achieve the task.`,
  tools: server.tools(),
});

first start with stdio

[leehuwuj]

#1819 having some trouble with SSE:

1. @modelcontextprotocol/sdk fails in CommonJS projects due to incompatible ESM-only dependency (pkce-challenge) modelcontextprotocol/typescript-sdk#217
2. Even with a manual fix for 1., the client is still not connect to the sever through sse (no network issue):

Error: Not connected
    at SSEClientTransport.send (./node_modules/.pnpm/@modelcontextprotocol+sdk@1.8.0/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:210:13)