Support redirecting stdout/stdin/stderr to/from other sources

[marco-souza]

Description

This PR implements stdin, stdout, and stderr redirects.

This PR continues the work made by @jtolio at https://github.com/Shopify/go-lua/pull/43 🙏

Changes

• added initial implementation
• moved test packages to avoid conflicts
• created test cases to validate redirect
• added a lib to facilitate assertions (lmk if I should remove it)

Note: stderr is not being used in our code, the current implementation returns the error as a value. Therefore, stderr can be removed, but I left it for consistency.

I'm looking forward to your feedback!