Implement a macro for eas{y,ier} creation of interface and socket set on bare-metal

[whitequark]

Right now the way lifetimes are handled requires some very unobvious contortions. Here's the ionpak code: https://github.com/m-labs/ionpak/blob/4347ddc5379594b299e1fa6c294449e01cc27b78/firmware/src/main.rs#L158-L192