Generate different types for scalar and memory values

Currently, `cgeist` generates the same types for scalar and memory values, so compiling:

```cpp
class wrapper {
public:
explicit wrapper(bool b) : b{b} {}
private:
const bool b;
};

wrapper wrap(bool b) { return wrapper{b}; }
```

using `clang` results in a function signature like:

```llvm
define dso_local i8 @_Z4wrapb(i1 noundef zeroext %b)
```

whereas `cgeist` compiles to:

```llvm
define { i8 } @_Z4wrapb(i8 %0)
```

**Describe the solution you would like**

`cgeist` codegen should mimic `clang`'s in that aspect.

**Describe alternatives you have considered**

Handling this in a pass, but it would probably overcomplicate things and not save any time if a different codegen is used (it could already handle the problem).