chore(arbitrator): generate forward_stub at compile time

[bernard-wagner]

Another chore to get arbitrator closer to being usable as a dependency and not need to run make locally first (brotli is the other major build dependency).

The forward_stub.wasm that was generated during make is no longer necessary, but I kept it for consistency.

Removes the need to run wat_to_wasm on the output of wasm-libraries/forward.

[bernard-wagner]

@eljobe I will look at why the CI is failing. Encountered this issue before and was certain I resolved it.

Do you have cloud-config or some other script used to create the arbitrator-ci worker? I kind of reverse-engineered it and I am using LXC containers to run the instances locally for my fork.