add client configuration allow_attester_search_only_for_domains

[tomholub]

What about adding allow_attester_search_only_for_domains option?

If it's set then app will ignore disallow_attester_search_for_domains option and search only in listed domains.

Plus add an appropriate test.

Originally posted by @tomholub in FlowCrypt/flowcrypt-ios#1668 (comment)