stdlib: Add input function

[spotandjake]

In python there is the input function which makes reading inputs syncronously from the command line super easy. This helps to position python in an especially useful place for learning to program and writing simple interactive programs. It would be great if we could add a function like this, currently this behaviour could be done through stdin but exposing a nice user friendly function would greatly help with developer experience.

I think the desired type for this would be input(prompt="") => string, if we ever get async capabilities in grain, it would also be great if this was an async function.

We may want to consider adding some sort of console library that contains functions like this and possibly additional printing utils like printTable.

[ospencer]

Requires #1583

[ospencer]

I also agree that this should be in its own library, including things like readLine, etc.