[libos] Enhancement: Update imports in NetworkLibOS

[carvalhof]

This PR updates SharedNetworkLibOS import in NetworkLibOS.

[carvalhof]

LGTM. I'm a little confused why this even compiled for the other libOSes.

Actually, if you make LIBOS=catnip, for instance, it's OK. However, if you change Cargo.toml:

from

[features]
default = ["catnap-libos"]

to

[features]
default = ["catnip-libos"]

and make LIBOS=catnip

you got this error:

error[E0412]: cannot find type SharedNetworkLibOS in this scope --> src/rust/demikernel/libos/network/mod.rs:57:12 | 57 | Catnip(SharedNetworkLibOS<SharedInetStack<SharedDPDKRuntime>>), | ^^^^^^^^^^^^^^^^^^ not found in this scope

This error occurs even using catnip, catpowder, and catloop on Cargo.toml.