Blender Git Loki

Fixes and edits to studio light operators

- Remove pathlib use
(was converting to/from string with no real advantage).
- Use user_resource(..., create=True) to ensure the path exists.
- Pass full path to BKE_studiolight_create, don't add extension after.
- Fix 'sl' filtering glob and move from ui code to operator.
- Fix string copy length.