This came up in #106591 which reported that changing a Light Group would
not work when alt-clicking the property field (which is the usual method
to edit a property for multiple objects at once).
This is because string properties were not supported in
`ui_selectcontext_apply` which is now done.
Similar to 1318660b04 [which added support for pointer properties].
Adding general support for string properties means this method can now
be used for many more things:
- changing all sorts of ID names (objects, meshes, ...)
- many settings in modifiers (e.g. vertexgroups)
- geometry nodes modifier properties (e.g. attribute names)
- ...
Fixes#106591
Philipp Oeser