Under certain circumstances, the library symbol links were missing
the library nickname causing the schematic symbols to appear as if
the library symbol was missing.
Added a helper function to create the symbol library name to avoid
code duplication.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/17143
The IO_RELEASER is a thin-wrapper around a std::unique_ptr, but done
this way to allow easier addition of a custom deleter in the future if
something needs to call back into the IO_MGR.