Gen variable code

# Diff located here: https://github.com/rapid-lang/rapid/compare/8b7b1761608f90f7b9dc9478ac2095b9a31cfc41...gen

Prints a valid Golang file for integer variable declarations, assignments and `println`'s.
Is fully up to date with the SAST in terms of what statements are supported.

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## Testing

Diffs the output against the expected output.

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Things that look strange but aren't:

- Go requires that we use every variable
  - assigning them to `_` counts as a use so all variables are assigned to `_` after declaration
- Also must use every package
  - assign one function from the package to `_`