In case a 'compatible' old IDProperty exists,
`update_input_properties_from_node_tree` would essentially reuse it
as-is, only keeping the UI data from the freshly new IDProp it created
for the socket.
This commit instead fully re-use the newly created idprop, only copying
(and converting as needed) the value from the old one.
That way, we can be sure that the actual type of the IDProperty is reset
to its expected type, instead of being kept forever in a 'wrong' type.
Having IDProps in a stable, expected type is a sounder behavior in
general, and critical for lower-levels of code to work as expected
(like RNA diffingi, and by extension, Library Overrides e.g.)
NOTE: This is a side-finding from work on #122743 to make some idprops
statically typed, and is a pre-requirement for this to work with the
GeoNodes modifiers case.
Pull Request: https://projects.blender.org/blender/blender/pulls/122876
57669600b1