feat: add /status endpoint

[TomasArrachea]

Closes #794.

This PR adds a new /status endpoint on the store, block-producer and RPC components. The RPC endpoint hits the store and block-producer and aggregates their status into a single status response:

{
    "version": "0.9.0",
    "store_status": {
        "version": "0.9.0",
        "status": "connected",
        "chain_tip": 684
    },
    "block_producer_status": {
        "version": "0.9.0",
        "status": "connected"
    }
}

This endpoint can be easily accesed using Postman or grpcurl.

To run using grpcurl:

grpcurl -import-path ./proto/proto -proto rpc.proto -plaintext localhost:57291 rpc.Api.Status

[sergerad]

Nice work. Thanks for including the grpcurl command. Branch works as expected 👍

[bobbinth]

Looks good! Thank you!

We should also update documentation (at least here but maybe also worth mentioning it in other places).