vendor: remove bytecode libraries, and split the package

[inclyc]

@Aleksanaa @Atemu would you like to review libnixf, libnixt default.nix as their package?

This made nixd possible being built as separate derivations, libnixf, libnixt may be made for standalone uses.

[inclyc]

I can't comment on the C++ parts but the Nix drvs LGTM.

How about meson files & generated pkg-config?

[Atemu]

Not proficient in those either, sorry.