For some reason we have a whole bunch of redundant icons for linked data and library overrides.
These link icons are redundant (only one of each type should be kept):
- `LINKED`
- `DECORATE_LINKED` (unused)
- `LINK_BLEND`
Same with these library override icons:
- `LIBRARY_DATA_OVERRIDE`
- `DECORATE_LIBRARY_OVERRIDE` (only used in custom properties UI, could be replaced easily)
Also, the `RESTRICT_INSTANCED_OFF` icon looks like thicker version of the linked icon. It and its ``RESTRICT_INSTANCED_ON` counterpart are not used.