Define publicity at a per-binding level, not per-symbol (#57094)
Symbols don't belong to modules and can't be marked public. The
statement `public Fix` in Base does not make the symbol `:Fix` public
everywhere. My package's `Package.Fix` may still be private. It's
bindings that are marked this way:
https://github.com/JuliaLang/julia/blob/fa9478b5178052ef00690732fe363601182b6922/src/julia.h#L695-L705
