client: fibo example is slow

[EdAyers]

@experiment
def fibo(n):
    print(f"computing fibo({n})")
    if n < 3:
        return 1
    else:
        return fibo(n - 1) + fibo(n - 2)


print(fibo(50))

Takes ages because it is pickling and unpickling these numbers.
There are a few things slowing this down:

• Eval uploads should be batched or async streamed.
• Even if the eval is stored locally, it needs to be unpickled from the local cache. There should be special support for basic scalar result types like strings and numbers.
• There should be an @cache in-mem cache too. At least a weakref system.