During object duplication the syncing is temporarily disabled.
With {D15885} this isn't useful as when disabled the view_layer
is still accessed to locate bases. This can be improved by first
locating the source bases, then duplicate and sync and locate
the new bases.
This patch removes the resync forbid and improve the times
that resyncing actually must happen.
Reviewed By: mont29
Maniphest Tasks: T73411
Differential Revision: https://developer.blender.org/D15886