Make sync worker run less frequently when auto upload folder requirements are not met  #13078

The sync background worker is currently running regularly in the background and scanning the file system for changed files. As some people point out (e.g. #13008) that is sometimes not wanted when the requirements for the autoupload folder (e.g. only upload in Wi-Fi) are not met since it drains the Akku. The problem here is that the scanning should still take place to be able to have a current and up-to-date upload queue, where the changed files are listed. To produce a compromise, we could simply make the interval between file system scans larger when the requirements are not met. So for example when the mobile phone is not connected to unmetered Wi-Fi run the background worker only every 1h and not every 15 min.