testground/node/app: create PFD steps

[Bidon15]

Introduction 🖖

In both celestia-app and celestia-node, we can submit pfd. However, this is not a straightforward approach for both of them

Celestia Application part 🔧

In celestia-app, we can already use the wrapcli approach to fulfil plain PFD
Still, we need to implement opening of the grpc rpc endpoint from app to other celestia-node types such as light/full

Celestia Node part 🧱

Pre-Requisites 📦

• Celestia-App should find a way that the node is asking for funding the account
• Celestia-Node should check the balance before starting PFD

What needs to be done 🧐

In celestia-node, we are currently using the RPC approach
https://docs.celestia.org/developers/node-tutorial#connect-to-a-public-core-endpoint

We might need to wrap this RPC part as usually the user uses these APIs
https://docs.celestia.org/developers/node-tutorial#submit-a-pfd-transaction