Use readable string comparison for LLVM generator tests

[Ailrun]

Is your feature request related to a problem? Please describe.
Current LLVM-generator tests are nearly impossible to parse. When a problem occurs, it involves significant amount of mental energy to find what the problem is.

Describe the solution you'd like
Use more readable, line-separated, easy-to-diff strings instead of unparsible data type.

Additional context
Is there any case that a stringification mangles different data types into the same string?

[Ailrun]

Or are there any other testing frameworks that support an error-formatting functionality?

[Ailrun]

I think if there is any pretty print library for LLVM, a single newtype wrapper would solve the problem, by defining a custom Show instance.