Fix building of callgraph including preloaded symbols (GH-15545)

This issue was introduced in GH-15021. When building the call graph, we can now
see preloaded functions. However, buildin

Fix building of callgraph including preloaded symbols (GH-15545)

This issue was introduced in GH-15021. When building the call graph, we can now
see preloaded functions. However, building the call graph involves adding the
function to the caller list of the callee, which we don't want to do for
functions not coming from the script.

Fixes GH-15490

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