New setting to preselect only personal collections (bitfireAT/davx5#276)

* Add new preselect_collections option and deprecate sync_all_collections option

* Optimize imports

* At refresh, decide on whether a collection should be preselected

* Add preselect_collections_blacklist setting and restriction

* Adhere to preselect_collections_blacklist setting

* Add preselect_collections values

* Also check for empty regex string and use new setting values

* Add unit tests

* Remove sync_all_collections setting and restriction

* Blacklist nextclouds recently contacted addressbook in restriction and setting by default

* Improve kdoc

* KDoc, changed setting names, minor code optimizations

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