4934: Remove special casing for library symbols r=matklad a=matklad
We might as well handle them internally, via queries.
I am not sure, but it looks like the current LibraryData setup might
even predate salsa? It's not really needed and creates a bunch of
complexity.
bors r+
🤖
Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>