Add CLIF to `wasmtime explore` output

[fitzgen]

(When using Cranelift.)

When I originally implemented wasmtime explore we didn't have a good way to get the CLIF. But since then we've added the --emit-clif CLI flag, so I suspect it is easier to get now than it was then. Would be very cool to have three panes, and the color-coded mapping between them synchronized: (1) wasm (2) clif (3) asm

[vulc41n]

I did it on my fork, should I submit a pull request ? 🙂

[fitzgen]

Yes please!