[native] Add loading button state to CreateSIWEBackupMessageBase

Summary:
Noticed that when the user presses the button to open SIWEPanel, we don't change the button to a loading state like we do for the ConnectEthereum screen here.

This diff adds the loading state to the button, which improves the responsiveness of the UX.

Test Plan: I tested in my local environment to make sure the button changed to a loading state

Reviewers: will, varun

Reviewed By: varun

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13804