Code `Func`s should take in `Symbol`s for their "names" instead of raw Strings

[balacij]

No, it doesn't have to be String. Thinking about it, it should indeed be implementation-level symbol. Well spotted!

Originally posted by @JacquesCarette in https://github.com/JacquesCarette/Drasil/pull/2952#discussion_r835765944

The discussion originates from the above comment on a PR. However, we might also consider creating a separate "symbol" language for solely "code"-like things (so as to not allow invalid constructions [e.g., those with UTF characters are still typically unusable in many programming languages]).