Commit 6b6ff58d3c4a ("Part: Rename AttachExtension::Support property to
AttachmentSupport...") provided code to convert property name when loading
files saved with previous versions. Unfortunately a41f176f596a
("Toponaming: bring in missing code fragments in Part") was based on
at the time obsolete code which did not contain before mentioned tweak,
so AttachmentSupport ended unassigned.
Fixes: a41f176f596a ("Toponaming: bring in missing code fragments in Part")
This is added to conveniently change the attacher type of a Part object.
Hint: A new property is used to avoid to break project files when opening it with an older version.
See also forum thread: https://forum.freecad.org/viewtopic.php?t=87891
ViewProviderAttachExtension::extensionMergeOverlayIcons() calls
AttachExtension::positionBySupport() which will always touch the
extended object. This may cause recomputation problems, e.g a datum
that is always touched, because normal recomputation trigger tree
view update by a timer, tree view refreshes the icon, datum gets
touched again.
AttachableObjects are desired in multiple occasions, and the current AttachableObject is not flexible enough to handle all cases. Hence the code is portet to an extension, which gives the needed flexibility.
