fbb4a7eb43
This enables calling code to deal with the blendfile handle themselves, BKE_blendfile_link then just borrows, uses this handle and does not release it. Needed e.g. for python's libcontext system to use new BKE_blendfile_link_append code. Part of T91414: Unify link/append between WM operators and BPY context manager API, and cleanup usages of `BKE_library_make_local`.