[Feat]: Inspection of gRPC A2A agents

### Is your feature request related to a problem? Please describe.

The inspector expects JSON-RPC agent. I doesn't work with a gRPC A2A agent.

Error: An internal server error occurred: HTTP Error 503: Network communication error fetching agent card from http://localhost:50051/.well-known/agent.json: illegal request line

This error is due to the fact that my agent is not exposing an HTTP endpoint for the card, but it expects to receive GetAgentCard gRPC call.

### Describe the solution you'd like

Extend the inspector to inspect gRPC A2A agents

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct