Consider dropping libgfold and collapsing into one crate

[nickgerace]

As of the time of writing, libgfold's only user is gfold according to crates.io.

The purpose of libgfold was to expose gfold internals for external consumption. Given the steady popularity of gfold itself, the lack of external users of libgfold and the potential de-bloating opportunities that using a single crate offers (e.g. using anyhow everywhere), it might be worth consolidating everything down to one crate.

[nickgerace]

@uncenter do you have any thoughts here? I know you had other things you wanted to contribute (thank you and no pressure to do so!), so I wanted to check with you.

[uncenter]

This sounds like a good idea yep! I can try consolidating it unless you have some specific details in mind.

[nickgerace]

Closed by #271