`BKE_lib_override_library_validate` used on fileread to ensure all
liboverrides are valid was using direct call to
`BKE_lib_override_library_free`. However, this was lacking the handling
of embedded dependencies (from liboverride PoV), in particular
ShapeKeys.
Since these shapekeys were still tagged as embedded liboverrides,
liboverride code would later assume their owner (mesh etc.) was also a
valid liboverride, leading to various potential issues.
Use instead `BKE_lib_override_library_make_local`, which also ensures
that embedded dependencies are handled properly.
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