Include address book account syncs, when querying sync status (bitfireAT/davx5#378)

* Use tags instead of uniqueWorkNames for work queries.

* Also include address book accounts, when querying sync status.

Give address book account sync workers their parent (main account) sync workers tag too, such that they will be included at the query for sync status of their parent account.

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Co-authored-by: Ricki Hirner <hirner@bitfire.at>