Display progress of monero-wallet-rpc download in GUI

[binarybaron]

We should display the progress of the download while the monero-wallet-rpc is being updated.

Adding an new variant to the TauriContextInitializationProgress enum would be the easiest way. We can then use it to display the already implemented MoneroWalletRpcUpdatingAlert.

#[typeshare]
#[derive(Display, Clone, Serialize)]
pub enum TauriContextInitializationProgress {
    # New variant here
    UpdatingMoneroWalletRpc(u16),
    OpeningBitcoinWallet,
    OpeningMoneroWallet,
    OpeningDatabase,
}