Integrate WKD search

[ekievsky]

This PR integrates PubLookup instead of RemoteContactsProvider

close#296

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Tests :

• Difficult to test. We need to add separate layer of Networking to be able to inject it into appropriate classes and "spy" it.

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[tomholub]

Looks good. It troubles me that we can't easily test this, particularly relies on #307