[Go] Add MCP plugin

[apascal07]

Describe the bug
There's no Go SDK by https://modelcontextprotocol.io/introduction but there is a highly used one here: https://github.com/mark3labs/mcp-go

We'd want to implement a server (expose Genkit tools/actions) and a client (take in tools/resources exposed by any server as Genkit tools).

JS implementation for reference: https://github.com/firebase/genkit/tree/702b6cf73e8763a80359b88ed3c6b4674504f517/js/plugins/mcp/src

[cziter15]

Thumbs up! It would be nice to weaponize LLM generation with MCP tools, for example - home assistant.
I've tried with mcp-go, but it has issues when comes to translation MCP -> Genkit Tool format.
Built-in support would be awesome.

[lgothard]

The Go tools team has started a MCP prototype ... unsure of release target

https://cs.opensource.google/go/x/tools/+/master:internal/mcp/README.md