feat(service_adguard_home): add the clients

[retransmit]

Next stage of AdGuard Home (#166): the Clients.

What it adds

• Clients tab in the bottom bar (Home, Query log, Clients) - the persistent clients with their identifiers, tags and queries, and the runtime clients with where the server learned of them. The lists are not read until the tab is opened
• A persistent client in a form - add, change, delete (confirmed). Identifiers, its own protection settings and safe search per search engine, its own blocked services, upstream servers and their cache, leaving it out of the query log or the statistics, tags
• Blocked services picked from the server's catalogue - by group, with icons and search, Block all and Unblock all
• Who is behind an address - a runtime client, a top client on Home and the client of a query open the same sheet, with Edit client or Add as persistent client, filled in

Notes

• A change is written over the client as the server has it at that moment, and only the settings that were changed in the form. What the form does not show, such as a pause schedule, is kept, and so is a setting someone changed elsewhere meanwhile
• A runtime client is only offered as a new persistent client once the server has said it is nobody's. Matched on the phone, a device a client names by its MAC address would look unowned
• The pause schedule of a client's blocked services is shown and kept, not edited. Its editor comes with the filters
• The sign-in rule holds on the new tab: one request for a wrong password, nothing while idle, one per Try again

Testing

532 tests in service_adguard_home and 200 in the app. Verified on an emulator against AdGuard Home v0.107.79, with every read and write compared with the server. The look was checked on a phone.

Not done yet: renaming or deleting a client does not touch custom rules that name it, so a block set "for this client only" stops applying after a rename; the "saved" message can be hidden under a query's sheet; at 320 dp the form's title is cut by a few pixels.