Improve user experience when blockchain client or service is indexing

[eniolam1000752]

What was the problem?

This PR resolves #5524

How was it solved?

• [x] Introduce page loader when service is indexing
• [x] Add unit tests

How was it tested?

• Ensure you run a local instance of core and service
• Restart both instance of core and service while you ensure the app is opened and it network is switched to the local network.
• When service and core is up and running you should see the indexing loading status show up and update as the progress proceeds.