Bundle workingset parts in object library

Also use a dedicated logging category in working set code.
Instead of SHELL the WORKINGSET category is used for logging. Partly,
because of duplicate symbols when linking, introduced by use of the
working set library.
1 job for !213 with working-sets in 32 minutes and 45 seconds (queued for 48 minutes and 13 seconds)
latest detached
Status Job ID Name Coverage
  Build
passed #107685
linux kf5-qt5 qt5.15

00:32:45

46.0%