feat: improve onboarding_cli resilience

[srieteja]

- What I did

• removed qr_code related components from code
• rename OnboardingUtil -> RegistrarApiUtil and consume this change
• Delete .atKeys file if onboarding process encounters an unrecoverable exception/error
• Retry each of the onboarding steps in case they encounter an exception

- How I did it

• Introduced _deleteAtKeys() which checks if the atsign is already onboarded, if not deletes the atKeys file that has been created
• Introduced OnboardingTask which is an abstract class that contains strucutre to retry a specific task in case it has encountered an Exception/Error or has not fetched necessary data. All the onboarding tasks have been rewritten by extending this class with varying maxRetries count to improve resilience.

- How to verify it

• activate_cli should be working as usual
• In case a certain task (updating pkamPubKey, encPubKey to remote) fails, onboarding_cli should retry those specific tasks. In case maxRetry count is exceeded, the .atKeys file should be deleted.
• Unit tests on the way

- Description for the changelog

• removed qr_code related components from code
• rename OnboardingUtil -> RegistrarApiUtil and consume this change
• Delete .atKeys file if onboarding process encounters an unrecoverable exception/error
• Retry each of the onboarding steps in case they encounter an exception

[srieteja]

Unit tests on the way

[gkc]

@srieteja What's the status of this PR?

[srieteja]

@gkc this PR is from before at_auth was introduced, so it requires some capacity to bring this PR up to speed. And since its not linked to a ticket anymore, it's low priority for me. Will bring this up to speed and get it closed as soon as I find some time.

[gkc]

@gkc this PR is from before at_auth was introduced, so it requires some capacity to bring this PR up to speed. And since its not linked to a ticket anymore, it's low priority for me. Will bring this up to speed and get it closed as soon as I find some time.

Makes sense, thanks @srieteja