Split between public provider and wallet client

Summary

We should split the provider in two components: a public provider used for non-authenticated requests, and a wallet client for interactions that require a wallet.

Background

At the moment, Starknet React deals with only a single instance of the provider. If the user didn't connect their wallet, the library uses the provider provided by the user (either a gateway provider or a jsonrpc provider). If the user connects their wallet, the library uses the provider provided by the wallet.

Problem

With the deprecation of the gateway and the switch to json-rpc, the current pattern is an issue because wallets shouldn't pay for dapps rpc calls.

On the other hand, decoupling the provider from the wallet means we need another mechanism for creating a provider based on the currently connected network.

Proposal

I propose to follow wagmi approach.

split the single provider in a public provider (for rpc calls etc) and a wallet client (for signing, sending tx)
users configure Starknet React with a provider factory and a list of supported chains.
by default:
- the exposed public provider is an instantiation of the provider for the default network
- the wallet client is undefined
after the user connects their wallet:
- the wallet client is the provider expose by the wallet
- the exposed public provider is an instantiation of the provider for the wallet's network
  - when the user changes the network:
  - re instantiate the public provider to connect to the new network
  - if the user switches to a network not supported by the dapp (not sure about this)
  - change current provider to default (to avoid too many errors in the app)
  - return an error somewhere, for example in usePublicProvider so that the dapp can display an error message

apibara / starknet-react